Low-color scratch-resistant articles with a multilayer optical film
Embodiments of this disclosure pertain to articles that exhibit scratch-resistance and improved optical properties. In some examples, the article exhibits a reflection or transmission color shift of about 2 or less, when viewed at an incident illumination angle in the range from about 20 degrees to about 60 degrees from normal under an illuminant and hardness of at least 14 GPa at an indentation depth of at least 100 nm from the surface of the article. In one or more embodiments, the articles include a substrate, and an optical film disposed on the substrate. The optical film includes a scratch-resistant layer and an optical interference layer. The optical interference layer may include one or more sub-layers that exhibit different refractive indices. In one example, the optical interference layer includes a first low refractive index sub-layer, a second a second high refractive index sub-layer, and an optional third sub-layer.
1. An article comprising:
a substrate having a surface and comprising a glass, a glass-ceramic, or single-crystal sapphire; and
an optical film disposed on the substrate surface forming a coated surface, the optical film comprising a scratch-resistant layer and an optical interference layer disposed between the scratch-resistant layer and the substrate;
wherein the article comprises a hardness of about 14 GPa or greater, as measured by indenting the coated surface with a Berkovich indenter to form an indent having an indentation depth of at least about 100 nm from the surface of the coated surface,
wherein the article exhibits a reflection or transmission color shift of about 2 or less, when viewed at an incident illumination angle in the range from about 20 degrees to about 60 degrees from normal incidence under an International Commission on Illumination illuminant selected from the group consisting of A series illuminants, B series illuminants, C series illuminants, D series illuminants, and F series illuminants, wherein color shift is calculated using the equation √((a* 2 −a* 1 ) 2 +(b* 2 −b* 1 ) 2 ), with a* 1 and b* 1 representing the coordinates of the article when viewed at normal incidence and a* 2 and b* 2 representing the coordinates of the article when viewed at the incident illumination angle.
2. The article of claim 1 , wherein the optical interference layer comprises a first low refractive index RI sub-layer and a second high RI sub-layer.
3. The article of claim 2 , wherein the difference between the refractive index of the first low RI sub-layer and the refractive index of the second high RI sub-layer is about 0.01 or greater.
4. The article of claim 1 , wherein the optical interference layer comprises a plurality of sub-layer sets, the plurality of sub-layer sets comprising a first low RI sub-layer and a second high RI sub-layer.
5. The article of claim 4 , wherein the optical interference layer further comprises a third sub-layer disposed between at least one of:
the plurality of sub-layer sets and the scratch-resistant layer; and
the substrate and the plurality of sub-layer sets, and
wherein the third sub-layer has a RI between the refractive index of the first low RI sub-layer and the refractive index of the second high RI sub-layer.
6. The article of claim 4 , wherein the optical interference film comprises up to about 10 sub-layer sets.
7. The article of claim 4 , wherein at least one of the first low RI sub-layer and the second high RI sub-layer comprises an optical thickness (n*d) in the range from about 2 nm to about 200 nm.
8. The article of claim 1 , wherein the optical interference layer comprises a thickness of about 800 nm or less.
9. The article of claim 1 , wherein the optical interference layer comprises an average light reflection of about 0.5% or less over the optical wavelength regime.
10. The article of claim 1 , wherein the article exhibits an average transmittance or average reflectance having an average oscillation amplitude of about 5 percentage points or less over the optical wavelength regime.
11. The article of claim 1 , wherein the article exhibits a surface hardness of about 16 GPa or greater, as measured on the coated surface by indenting the coated surface with a Berkovitch indenter to form an indent having an indentation depth of at least about 100 nm from the surface of the coated surface.
12. The article of claim 1 , wherein the amorphous substrate comprises a glass selected from the group consisting of soda lime glass, alkali aluminosilicate glass, alkali containing borosilicate glass and alkali aluminoborosilicate glass.
13. The article of claim 12 , wherein the glass is chemically strengthened and comprises a compressive stress (CS) layer with a surface CS of at least 250 MPa extending within the chemically strengthened glass from a surface of the chemically strengthened glass to a depth of layer (DOL) of at least about 10 μm.
14. An article comprising:
a substrate comprising a substrate surface and comprising a glass, a glass-ceramic, or a single-crystal sapphire; and
an optical film disposed on the substrate surface forming a coated surface,
wherein the optical film comprises a scratch-resistant layer and an optical interference layer disposed between the scratch-resistant layer and the substrate, the optical interference layer comprising at least one set of sub-layers, the set of sub-layers comprising a first low RI sub-layer and a second high RI sub-layer,
wherein the article comprises a hardness in the range from about 14 GPa to about 50 GPa as measured by indenting the coated surface with a Berkovitch indenter to form an indent having an indentation depth of at least about 100 nm from the surface of the coated surface,
wherein the article comprises a reflection or transmission color shift of less than about 2, when viewed at an incident illumination angle in the range from about 20 degrees to about 60 degrees from normal incidence under an International Commission on Illumination F2 illuminant, and
wherein color shift is calculated using the equation √((a* 2 −a* 1 ) 2 +(b* 2 −b* 1 ) 2 ), with a* 1 , and b* 1 representing the coordinates of the article when viewed at normal incidence and a* 2 , and b* 2 representing the coordinates of the article when viewed at the incident illumination angle.
15. The article of claim 14 , wherein the first low RI sub-layer comprises at least one of SiO 2 , Al 2 O 3 , GeO 2 , SiO, AlO x N y , SiO x N y , Si u Al v O x N y , MgO, MgF 2 , BaF 2 , CaF 2 , DyF 3 , YbF 3 , YF 3 , and CeF 3 , and wherein the second high RI sub-layer comprises at least one of Si u Al v O x N y , Ta 2 O 5 , Nb 2 O 5 , AlN, Si 3 N 4 , AlO x N y , SiO x N y , HfO 2 , TiO 2 , ZrO 2 , Y 2 O 3 , Al 2 O 3 , and MoO 3 .
16. The article of claim 14 , wherein the scratch-resistant layer comprises at least one of AlN, Si 3 N 4 , AlO x N y , SiO x N y , Al 2 O 3 , SixCy, Si x O y C z , ZrO 2 , TiO x N y , diamond, diamond-like carbon, and Si u Al v O x N y .
17. The article of claim 14 , wherein the article further comprises a crack mitigating layer.
18. The article of claim 1 , wherein the illuminant comprises an F2 illuminant.
19. The article of claim 1 , wherein the incident illumination angle is in the range from about 30 degrees to about 60 degrees from normal incidence.
20. The article of claim 19 , wherein the illuminant comprises an F2 illuminant.
21. The article of claim 1 , wherein the incident illumination angle is in the range from about 40 degrees to about 60 degrees from normal incidence.
22. The article of claim 21 , wherein the illuminant comprises the illuminant comprises an F2 illuminant.
23. The article of claim 14 , wherein the incident illumination angle is in the range from about 30 degrees to about 60 degrees from normal incidence.
24. The article of claim 14 , wherein the incident illumination angle is in the range from about 40 degrees to about 60 degrees from normal incidence.
25. The article of claim 1 , wherein the substrate exhibits substrate transmitted a* and b* color coordinates and the article exhibits article transmitted a* and b* color coordinates, both under D65 illumination at 5 degrees,
wherein the article transmitted a* color coordinate varies from the substrate transmitted a* color coordinate by less than +/−0.1, and
wherein the article transmitted b* color coordinate varies from the substrate transmitted b* color coordinate by less than +/−0.4.