Electronic device coatings for reflecting mid-spectrum visible light
An electronic device may include conductive structures having a visible-light-reflecting coating. The coating may include a seed layer, transition layers, a neutral-color base layer, and an uppermost layer that forms a single-layer interference film. The neutral-color base layer may be opaque to visible light. The interference film may include silicon and may have an absorption coefficient between 0 and 1. The interference film may include, for example, CrSiN or CrSiCN. The composition of the interference film, the thickness of the interference film, and/or the composition of the base layer may be selected to provide the coating with a desired color near the middle of the visible spectrum (e.g., at green wavelengths). The color may be relatively stable even if the thickness of the coating varies across its area.
1. An electronic device, comprising:
a conductive structure; and
a visible-light-reflecting coating on the conductive structure, the visible-light-reflecting coating comprising:
adhesion and transition layers on the conductive structure,
a neutral-color base layer on the adhesion and transition layers, and
a single-layer interference film on the neutral-color base layer, the single-layer interference film comprising silicon.
2. The electronic device defined in claim 1 , wherein the single-layer interference film comprises CrSiN.
3. The electronic device defined in claim 2 , wherein the neutral-color base layer comprises CrSiCN.
4. The electronic device defined in claim 1 , wherein the single-layer interference film comprises CrSiCN.
5. The electronic device defined in claim 4 , wherein the neutral-color base layer comprises CrSiCN and wherein the single-layer interference film forms an upper-most layer of the visible-light-reflecting coating.
6. The electronic device defined in claim 5 , wherein an atomic percentage of Si atoms in the neutral-color base layer is between 30% and 60%, wherein an atomic percentage of Cr atoms in the neutral-color base layer is between 1% and 40%, wherein an atomic percentage of C atoms in the neutral-color base layer is between 15% and 65%, and wherein an atomic percentage of N atoms in the neutral-color base layer is between 0.5% and 15%.
7. The electronic device defined in claim 1 , wherein the single-layer interference film comprises a material selected from the group consisting of: AlTiSiN and TiSiN.
8. The electronic device defined in claim 1 , wherein the neutral-color base layer is opaque, has an L* value between 48 and 62, an |a*| value less than 2, and a |b*| value less than 2.
9. The electronic device defined in claim 1 , wherein the single-layer interference film has a thickness between 50 nm and 150 nm.
10. The electronic device defined in claim 9 , wherein the visible-light-reflecting coating has a thickness between 1.2 microns and 1.8 microns, the single-layer-interference film has a first index of refraction, the neutral-color base layer has a second index of refraction that is greater than the first index of refraction, and the single-layer-interference film has an absorption coefficient that is greater than 0 and less than 1.
11. The electronic device defined in claim 1 , wherein the adhesion and transition layers comprise a seed layer on the conductive structure and a transition layer on the seed layer, wherein the seed layer comprises a material selected from the group consisting of: Cr, CrSi, and Ti, and wherein the transition layer comprises a material selected from the group consisting of: CrSiN, CrSiCN, CrN, and CrCN.
12. The electronic device defined in claim 1 , wherein the conductive structure has a three-dimensional surface and wherein the visible-light-reflecting coating is deposited on the three-dimensional surface.
13. Apparatus comprising:
a conductive substrate; and
a coating on the conductive substrate that configures the conductive substrate to exhibit a color, the coating comprising:
adhesion and transition layers on the conductive substrate,
an CrSiCN layer on the adhesion and transition layers, the CrSiCN layer being opaque to light of the color, and
an uppermost layer on the CrSiCN layer, the uppermost layer comprising CrSiN.
14. The apparatus defined in claim 13 , wherein the uppermost layer forms an interference film and the color comprises a wavelength between 500 nm and 600 nm.
15. The apparatus defined in claim 14 , wherein an atomic percentage of Cr atoms in the uppermost layer is less than 10% and wherein an atomic percentage of Si atoms in the uppermost layer is between 5% and 20%.
16. The apparatus defined in claim 14 , wherein an atomic percentage of Si atoms in the CrSiCN layer is between 30% and 60%, wherein an atomic percentage of Cr atoms in the CrSiCN layer is between 1% and 40%, wherein an atomic percentage of C atoms in the CrSiCN layer is between 15% and 65%, and wherein an atomic percentage of N atoms in the CrSiCN layer is between 0.5% and 15%.
17. The apparatus defined in claim 14 , wherein the adhesion and transition layers comprise a seed layer on the conductive substrate and a transition layer on the seed layer, wherein the seed layer comprises a material selected from the group consisting of: Cr, CrSi, and Ti, and wherein the transition layer comprises a material selected from the group consisting of: CrSiN, CrSiCN, CrN, and CrCN.
18. An electronic device comprising:
a conductive housing wall; and
a coating on the conductive housing wall, the coating comprising:
adhesion and transition layers on the conductive housing wall,
an CrSiCN layer on the adhesion and transition layers, the CrSiCN layer being opaque to visible light, and
an uppermost layer that forms an interference film for the visible light and that comprises CrSiCN.
19. The electronic device defined in claim 18 , wherein an atomic percentage of Cr atoms in the uppermost layer is less than 10%, wherein an atomic percentage of Si atoms in the uppermost layer is between 5% and 20%, and wherein an atomic percentage of N atoms in the uppermost layer is between 10% and 15%.
20. The electronic device defined in claim 18 , wherein the CrSiCN layer has an L* value between 48 and 62, an |a*| value less than 2, and a |b*| value less than 2.
21. The electronic device defined in claim 18 , wherein an atomic percentage of Cr atoms in the uppermost layer is between 20-30%, wherein an atomic percentage of Si atoms in the uppermost layer is between 50% and 60%, wherein an atomic percentage of N atoms in the uppermost layer is between 10% and 20%, wherein an atomic percentage of Cr atoms in the CrSiCN layer is between 30% and 40%, wherein an atomic percentage of Si atoms in the CrSiCN layer is between 50% and 60%, and wherein an atomic percentage of N atoms in the CrSiCN layer is between 10% and 20%.
22. The electronic device defined in claim 21 , wherein the uppermost layer has a thickness between 0.01 and 0.05 microns and wherein the coating has an L* value between 30 and 40, an a* value between 0 and 5, and a b* value between −10 and 0.
23. The electronic device defined in claim 18 , wherein an atomic percentage of Cr atoms in the uppermost layer is between 30-40%, wherein an atomic percentage of Si atoms in the uppermost layer is between 20% and 30%, and wherein an atomic percentage of N atoms in the uppermost layer is between 30% and 40%.
24. The electronic device defined in claim 23 , wherein the uppermost layer has a thickness between 0.05 and 0.07 microns and wherein the coating has an L* value between 40 and 50, an a* value between −5 and 0, and a b* value between −5 and −15.