Optical article having a temperature-resistant anti-reflection coating with optimized thickness ratio of low index and high index layers
View Patent ↗The present invention relates to an optical article having anti-reflection properties and high thermal resistance, comprising a substrate having at least one main face coated with a multi-layer anti-reflection coating comprising a stack of at least one high refractive index layer and at least one low refractive index layer, wherein the ratio: R T = sum of the physical thicknesses of the low refractive index layers of the anti - reflection coating sum of the physical thicknesses of the high refractive index layers of the anti - reflection coating is higher than 2.1. If the anti-reflection stack comprises at least one low refractive index layer having a physical thickness ≧100 nm which is not the outermost layer of the anti-reflection coating, said relatively thick layer and the underlying layers are not taken into account in R T calculation.
1. An optical article having anti-reflection properties comprising a substrate having at least one main face coated with a multi-layer anti-reflection coating comprising a stack of at least one high refractive index layer and at least one low refractive index layer, wherein:
each low refractive index layer has a refractive index of 1.55 or less;
each high refractive index layer has a refractive index higher than 1.55 and does not comprise niobium pentoxide (Nb 2 O 5 );
said coated main face of the optical article has a mean luminous reflection factor Rv ≦1%; and:
(a) the low refractive index layers of the anti-reflection coating below the outermost layer of said coating each have a physical thickness <100 nm, the ratio
R
T
=
sum
of
the
physical
thicknesses
of
the
low
refractive
index
layers
of
the
anti
-
reflection
coating
sum
of
the
physical
thicknesses
of
the
high
refractive
index
layers
of
the
anti
-
reflection
coating
is higher than 2.1, and the anti-reflection coating does not comprise a sub-layer comprising niobium (Nb); or
(b) the anti-reflection coating comprises:
at least one low refractive index layer having a physical thickness ≧100 nm which is not the outermost layer of the anti-reflection coating; and
at least one high refractive index layer and at least one low refractive index layer, which are located above the low refractive index layer having a physical thickness ≧100 nm and not being the outermost layer of the anti-reflection coating which is the furthest from the substrate, and the ratio
R
T
=
sum
of
the
physical
thicknesses
of
the
low
refractive
index
layers
of
the
anti
-
reflection
coating
sum
of
the
physical
thicknesses
of
the
high
refractive
index
layers
of
the
anti
-
reflection
coating
is higher than 2.1, with the proviso that the layers of the anti-reflection coating taken into account for the calculation of said ratio RT are only the layers located above the low refractive index layer having a physical thickness ≧100 nm and not being the outermost layer of the anti-reflection coating which is the furthest from the substrate.
2. The optical article of claim 1 , wherein the anti-reflection coating (b) does not comprise a sub-layer comprising niobium (Nb).
3. The optical article of claim 1 , wherein RT is higher than or equal to 2.15.
4. The optical article of claim 3 , wherein RT is higher than or equal to 2.2.
5. The optical article of claim 4 , wherein RT is higher than or equal to 2.25.
6. The optical article of claim 5 , wherein RT is higher than or equal to 2.3.
7. The optical article of claim 1 , further defined as having a critical temperature ≧75° C.
8. The optical article of claim 1 , wherein the high refractive index layers of the anti-reflection coating comprise at least one of TiO 2 , PrTiO 3 , or ZrO 2 .
9. The optical article of claim 1 , wherein at least one high refractive index layer of the anti-reflection stack comprises TiO 2 .
10. The optical article of claim 1 , wherein at least one low refractive index layer of the anti-reflection stack comprises a mixture of SiO 2 , and Al 2 O 3 .
11. The optical article of claim 1 , wherein all the low refractive index layers of the anti-reflection coating comprise a mixture of SiO 2 , and Al 2 O 3 , except the low refractive index layers of the sub-layer, if said anti-reflection coating comprises a sub-layer having at least one low refractive index layer.
12. The optical article of claim 1 , wherein the anti-reflection coating comprises a sub-layer.
13. The optical article of claim 12 , wherein the sub-layer is a SiO 2 based mono-layer sub-layer further defined as free of Al 2 O 3 .
14. The optical article of claim 12 , wherein the sub-layer is a multi-layer sub-layer consisting of:
one layer consisting of SiO 2 ; and
at most three layers interleaved between said layer consisting of SiO 2 and the substrate of the optical article.
15. The optical article of claim 12 , wherein the sub-layer consists of a thin layer of at least one metal or metal oxide having 10 nm thickness or less.
16. The optical article of claim 1 , wherein the anti-reflection coating comprises at least one electrically conductive layer.
17. The optical article of claim 16 , wherein the electrically conductive layer comprises at least one indium oxide, tin oxide, or zinc oxide.
18. The optical article of claim 16 , wherein the electrically conductive layer comprises indium-tin oxide.
19. The optical article of claim 1 , wherein the substrate is an organic or mineral glass substrate.
20. The optical article of claim 19 , wherein the substrate is an organic glass substrate having a thermal expansion coefficient of 50.10 −6 ° C. −1 to 180.10 −6 ° C. −1 .
21. The optical article of claim 1 , further defined as a finished or semi-finished lens.
22. The optical article of claim 1 , wherein the substrate comprises an abrasion- and/or scratch-resistant coating, an impact-resistant coating, or an impact-resistant coating coated with an abrasion- and/or scratch-resistant coating.
23. A method of manufacturing an optical article having anti-reflection properties, comprising:
providing an optical article having two main faces; and
forming on at least one main face of said optical article an anti-reflection coating of claim 1 by forming layers of the anti-reflection coating via vacuum deposition.
24. A method according to claim 23 , wherein the layers of the anti-reflection coating are deposited by vacuum evaporation.
25. A process for obtaining an optical article comprising a substrate having at least one main face coated with a multi-layer anti-reflection coating and having a critical temperature ≧75° C., wherein said anti-reflection coating exhibits a R T ratio higher than 2.1, R T being defined as:
R
T
=
sum
of
the
physical
thicknesses
of
the
low
refractive
index
layers
of
the
anti
-
reflection
coating
sum
of
the
physical
thicknesses
of
the
high
refractive
index
layers
of
the
anti
-
reflection
coating
and wherein:
the multi-layer anti-reflection coating comprises a stack of at least one high refractive index layer and at least one low refractive index layer;
each low refractive index layer has a refractive index of 1.55 or less;
each high refractive index layer has a refractive index higher than 1.55 and does not comprise niobium pentoxide (Nb 2 O 5 );
said coated main face of the optical article has a mean luminous reflection factor Rv ≦1%, and:
(a) the low refractive index layers of the anti-reflection coating below the outermost layer of said coating each have a physical thickness <100 nm and the anti-reflection coating does not comprise a sub-layer comprising niobium (Nb); or:
(b) the anti-reflection coating comprises:
at least one low refractive index layer having a physical thickness ≧100 nm which is not the outermost layer of the anti-reflection coating; and
at least one high refractive index layer and at least one low refractive index layer, which are located above the low refractive index layer having a physical thickness ≧100 nm and not being the outermost layer of the anti-reflection coating which is the furthest from the substrate; with the proviso that the layers of the anti-reflection coating taken into account for the calculation of said ratio RT are only the layers located above the low refractive index layer having a physical thickness ≧100 nm and not being the outermost layer of the anti-reflection coating which is the furthest from the substrate.
26. The process of claim 25 , wherein the anti-reflection coating (b) does not comprise a sub-layer comprising niobium (Nb).