Thin-film interference filter color coatings
An electronic device may be provided with conductive structures such as conductive housing structures. A visible-light-reflecting coating may be formed on the conductive structures. The coating may have adhesion and transition layers and a thin-film interference filter on the adhesion and transition layers. The thin-film interference filter may be a four-layer interference filter stacked directly onto the adhesion and transition layers and having an uppermost SiCrN layer, a lowermost SiN layer, and interleaved SiH and SiN layers. If desired, an opaque coloring layer such as a Cr layer may be disposed between the interference filter and the adhesion and transition layers. The coating may exhibit a deep red or orange color that has a relatively uniform visual response even when the underlying conductive structures have a three-dimensional shape.
1 . Apparatus comprising:
a conductive substrate; and
a coating on the conductive substrate and having a color, the coating comprising:
adhesion and transition layers, and
a thin-film interference filter on the adhesion and transition layers, wherein the thin-film interference filter has a lowermost layer that contacts the adhesion and transition layers and an uppermost layer opposite the lowermost layer, the uppermost layer comprises SiCrN, and the lowermost layer comprises SiN, and wherein the coating has, at a point of maximum thickness and a viewing angle of zero degrees, an L* value that is greater than 50, an a* value that is greater than 10, and a b* value that is greater than 40.
2 . The apparatus of claim 1 , wherein the thin-film interference filter is a five-layer thin-film interference filter.
3 . The apparatus of claim 2 , the thin-film interference filter further comprising:
a first SiH layer stacked on the lowermost layer;
an SiN layer stacked on the first SiH layer; and
a second SiH layer stacked on the SiN layer, the second SiH layer being interposed between the uppermost layer and the SiN layer.
4 . The apparatus of claim 3 , wherein the adhesion and transition layers comprise:
a CrSiN layer that contacts the lowermost layer of the thin-film interference filter; and
a Cr layer between the CrSiN layer and the conductive substrate.
5 . The apparatus of claim 3 , wherein the first SiH layer is thicker than the second SiH layer, the uppermost layer, the SiN layer, and the lowermost layer.
6 . The apparatus of claim 3 , wherein the uppermost layer has a first thickness between 20 nm and 50 nm, the first SiH layer has a second thickness between 30 nm and 60 nm, and the SiN layer has a third thickness between 10 nm and 30 nm.
7 . The apparatus of claim 6 , wherein the second SiH layer has a fourth thickness between 40 nm and 70 nm and the lowermost layer has a fifth thickness between 40 nm and 70 nm.
8 . The apparatus of claim 1 , wherein the apparatus comprises a wristwatch and the conductive substrate comprises a button on the wristwatch.
9 . Apparatus comprising:
a conductive substrate; and
a coating on the conductive substrate and having a color, the coating comprising:
adhesion and transition layers,
an opaque layer on the adhesion and transition layers, the opaque layer comprising chromium, and
a thin-film interference filter on the opaque layer, the thin-film interference filter having an uppermost layer comprising SiCrN, a lowermost layer comprising SiC, a first intermediate SiCrN layer on the lowermost layer, a first intermediate SiC layer on the first intermediate SiCrN layer, a second intermediate SiCrN layer on the first intermediate SiC layer, and a second intermediate SiC layer on the second intermediate SiCrN layer.
10 . The apparatus of claim 9 , wherein the thin-film interference filter is a six-layer interference filter.
11 . The apparatus of claim 10 , wherein the adhesion and transition layers comprise:
a CrSiN layer that contacts the lowermost layer of the thin-film interference filter; and
a TiN layer between the CrSiN layer and the conductive substrate.
12 . The apparatus of claim 9 , wherein the coating has, at a point of maximum thickness and a viewing angle of zero degrees, an L* value that is greater than 50, an a* value that is greater than 10, and a b* value that is greater than 40.
13 . The apparatus of claim 9 , wherein the apparatus comprises a wristwatch and the conductive substrate comprises a button on the wristwatch.
14 . An apparatus, comprising:
a conductive substrate; and
a coating on the conductive substrate and having a color, the coating comprising:
adhesion and transition layers, and
a thin-film interference filter on the adhesion and transition layers, wherein the thin-film interference filter has a first SiC layer, a first SiCrCN layer on the first SiC layer, and a second SiC layer on the first SiCrCN layer, an SiCrN layer on the second SiC layer, the SiCrN layer forming an uppermost layer of the thin-film interference filter, and the first SiC layer forming a lowermost layer of the thin-film interference filter.
15 . The apparatus of claim 14 , wherein the coating includes an opaque layer between the first SiC layer and the adhesion and transition layers, the opaque layer comprising titanium nitride.
16 . The apparatus of claim 14 , wherein the adhesion and transition layers comprise:
a CrSiN layer that contacts the first SiC layer; and
a Cr layer interposed between the CrSiN layer and the conductive substrate.