Optical article covered with a visible-absorbing, multi-layer anti-reflective coating, and production method thereof

1. An optical article comprising a transparent substrate made of organic or mineral glass, having main front and rear faces, at least one of said main faces comprising a multi-layer anti-reflection coating,

wherein said anti-reflection coating comprises at least two visible-absorbing layers comprising a sub-stoichiometric titanium oxide, the visible-absorbing layers being such that the relative transmission factor of visible light Tv is reduced by at least 10% compared with the same article not comprising said visible-absorbing layers, and

wherein the anti-reflection coating formed on at least one of the faces of the substrate comprises a stack of alternating high refractive index (HI) and low refractive index (LI) layers, wherein:

at least one of the visible-absorbing layers is a high index (HI) layer comprising a sub-stoichiometric titanium oxide, and

at least one of the low index (LI) layers comprises a mixture of silicon oxide and aluminum oxide.

2. The article of claim 1 , wherein the visible-absorbing layers are such that the relative transmission factor of visible light Tv is reduced by at least 40% compared with the same article not comprising said visible-absorbing layers.

3. The article of claim 1 , wherein the visible-absorbing layers have an extinction coefficient (k) equal to or greater than 0.2 for all wavelengths in the visible range from 380 to 780 nm.

4. The article of claim 1 , wherein the substrate is made of organic glass.

5. The article of claim 4 , wherein the organic glass substrate is made of polycarbonate.

6. The article of claim 1 , wherein the low refractive index layer (LI) comprising a mixture of silicon oxide and aluminum oxide is adjacent to a high refractive index (HI) visible-absorbing layer.

7. The article of claim 1 , wherein each of the high refractive index layers (HI) of the anti-reflection coating is a visible-absorbing layer made of sub-stoichiometric titanium oxide.

8. The article of claim 1 , wherein each of the low refractive index layers (LI) of the anti-reflection coating comprises a mixture of silicon oxide and aluminum oxide.

9. The article of claim 1 , wherein the SiO 2 /Al 2 O 3 low refractive index layer (LI) contains 1 to 5% by weight of Al 2 O 3 .

10. The article of claim 1 , wherein the anti-reflection stack comprises at least 4 layers.

11. The article of claim 10 , wherein the anti-reflection stack comprises the following layers:

25-35 nm of a mixture of sub-stoichiometric titanium oxides;

10-20 nm of SiO 2 doped with Al 2 O 3 ;

45-55 nm of a mixture of sub-stoichiometric titanium oxides;

40-50 nm SiO 2 doped with Al 2 O 3 ;

35-45 nm of a mixture of sub-stoichiometric titanium oxides; and

70-80 nm SiO 2 doped with Al 2 O 3 .

12. The article of claim 1 , wherein the sub-stoichiometric titanium oxide in the absorbent layers is given by the formula TiOx, wherein x is less than 2.

13. The article of claim 12 , wherein x varies from 0.2 to 1.2.

14. The article of claim 1 , wherein the sub-stoichiometric titanium oxide is obtained from a mixture of TiO and Ti 2 O 3 .

15. The article of claim 14 , wherein the weight ratio of TiO in the mixture of TiO and Ti 2 O 3 is at least 50%.

16. The article of claim 1 , further comprising an anti-scratch coating formed on the substrate, the anti-reflection coating being deposited onto said anti-scratch coating.

17. The article of claim 1 , wherein the anti-reflection coating is deposited exclusively on the rear face of the substrate.

18. The article of claim 1 , further defined as an ophthalmic glass.

19. The article of claim 1 , wherein the relative transmission factor of visible light Tv of said article is at most 40%.

20. A process for manufacturing the article of claim 1 , wherein all the layers of the anti-reflection stack are deposited by vacuum evaporation.