Optical article having a reflective coating with high abrasion-resistance
Disclosed is an optical article including a substrate having at least one main face coated with a reflective coating including a stack of at least one high refractive index layer having a refractive index higher than 1.55 and at least one low refractive index layer having a refractive index of 1.55 or less, in which the thicknesses of the layers in the reflective coating have been optimized according to specific design rules in order to boost the abrasion resistance of the optical article.
1. An optical article comprising:
a substrate having at least one main face coated with a reflective coating in the visible range comprising a stack of at least one high refractive index layer having a refractive index greater than 1.55 and at least one low refractive index layer having a refractive index of 1.55 or less, the refractive indexes being expressed for a wavelength of 550 nm,
wherein the reflective coating comprises at least four layers, and
the outermost low refractive index layer of the reflective coating has a physical thickness Tho of at least 10 nm,
the outermost high refractive index layer of the reflective coating has a physical thickness of 75 nm or less,
the penultimate low refractive index layer of the reflective coating, in a direction moving away from the substrate, has a physical thickness Thp of at least 150 nm,
the penultimate high refractive index layer of the reflective coating, in the direction moving away from the substrate, has a physical thickness ranging from 5 nm to 90 nm, and
Tho/4+Thp≥200 nm, or
wherein the reflective coating has exactly three layers, and
the outermost layer of the reflective coating is a low refractive index layer having a physical thickness of 70 nm or less,
the penultimate layer of the reflective coating, in the direction moving away from the substrate, is a high refractive index layer having a physical thickness of 50 nm or less, and
the first layer of the reflective coating is a low refractive index layer having a physical thickness of at least 200 nm, and
wherein the penultimate low refractive index layer of the reflective coating is the penultimate low refractive index layer within the low refractive index layers of the reflective coating,
wherein the penultimate high refractive index layer of the reflective coating is the penultimate high refractive index layer within the high refractive index layers of the reflective coating,
wherein high refractive index layers and low refractive index layers alternate with each other in the reflective coating, and
wherein, when determining the number of layers of the reflective coating, two or more adjacent high refractive index layers form a single high refractive index layer having a thickness equal to the sum of the thicknesses of individual layers of the two or more adjacent high refractive index layers, and two or more adjacent low refractive index layers are a single low refractive index layer having a physical thickness equal to the sum of the thicknesses of individual layers of the two or more adjacent low refractive index layers.
2. The optical article of claim 1 , wherein the optical article has a Bayer value determined in accordance with the ASTM F735-81 standard greater than or equal to 5.5.
3. The optical article of claim 1 , wherein the reflective coating has a number of layers greater than or equal to four, and the outermost low refractive index layer has a thickness of at least 70 nm.
4. The optical article of claim 1 , wherein the reflective coating has a number of layers greater than or equal to four, and the outermost low refractive index layer has a thickness ranging from 130 nm to 300 nm.
5. The optical article of claim 1 , wherein the reflective coating has a number of layers greater than or equal to four, and the penultimate low refractive index layer has a thickness ranging from 175 nm to 400 nm.
6. The optical article of claim 1 , wherein the reflective coating has a number of layers greater than or equal to four, and the penultimate high refractive index layer has a thickness ranging from 10 nm to 40 nm.
7. The optical article of claim 1 , wherein the reflective coating has a number of layers greater than or equal to four, and the penultimate low refractive index layer is thicker than the outermost low refractive index layer.
8. The optical article of claim 1 , wherein the reflective coating has three layers, and the first layer has a thickness ranging from 200 nm to 400 nm.
9. The optical article of claim 1 , wherein the reflective coating comprises the at least four layers, and
the outermost low refractive index layer of the reflective coating has the physical thickness of at least 200 nm,
the outermost high refractive index layer of the reflective coating has the physical thickness of 40 nm or less,
the penultimate low refractive index layer of the reflective coating, in a direction moving away from the substrate, has the physical thickness of at least 220 nm, and
the penultimate high refractive index layer of the reflective coating has the physical thickness ranging from 5 nm to 40 nm, or
wherein the reflective coating has exactly three layers, and
the outermost layer of the reflective coating is a low refractive index layer having the physical thickness of 50 nm or less,
the penultimate layer of the reflective coating is a high refractive index layer having the physical thickness of 50 nm or less, and
the first layer of the reflective coating is a low refractive index layer having the physical thickness of at least 250 nm.
10. The optical article of claim 1 , wherein the reflective coating comprises at least four layers, and
the outermost low refractive index layer of the reflective coating has the physical thickness of at least 230 nm,
the outermost high refractive index layer of the reflective coating has the physical thickness of 25 nm or less,
the penultimate low refractive index layer of the reflective coating has the physical thickness of at least 300 nm, and
the penultimate high refractive index layer of the reflective coating has the physical thickness ranging from 5 nm to 20 nm, or
wherein the reflective coating has three layers, and
the outermost layer of the reflective coating is a low refractive index layer having the physical thickness of 50 nm or less,
the penultimate layer of the reflective coating is a high refractive index layer having the physical thickness of 35 nm or less, and
the first layer of the reflective coating is a low refractive index layer having the physical thickness of at least 250 nm.
11. The optical article of claim 1 , wherein the mean light reflection factor on said at least one main face in the visible region Rv, defined in the ISO 13666:1998 standard, is greater than or equal to 8%.
12. The optical article of claim 1 , wherein the reflective coating has a number of layers lower than or equal to 10.
13. The optical article of claim 1 , wherein the reflective coating has a thickness ranging from 300 nm to 1 μm.
14. The optical article of claim 1 , wherein the high refractive index layers having the refractive index greater than 1.55 represent less than 20% of the thickness of the reflective coating.
15. The optical article of claim 1 , wherein the high refractive index layers having the refractive index greater than 1.55 represent less than 15% of the thickness of the reflective coating.
16. The optical article of claim 1 , wherein the reflective coating does not comprise any high refractive index layer having a physical thickness greater than or equal to 105 nm.
17. The optical article of claim 1 , wherein the optical article is an ophthalmic lens.
18. The optical article of claim 1 , wherein the reflective coating has at least one layer comprising Ti 3 O 5 .