Optical article comprising a precursor coating for an antifogging coating and a temporary layer rendering same suitable for edging

1. An optical article comprising a substrate, comprising:

at least one main surface coated with a first coating comprising, at the surface, silanol groups;

a second coating that is in direct contact with the first coating, and which is formed by deposition on the first coating, of at least one compound A comprising:

a polyoxyalkylene group; and

at least one group capable of establishing a covalent bond with a silanol group;

wherein the second coating is further defined as precursor for an antifog coating and comprises an internal part, in which compound A is grafted to the first coating, and an external part that can be removed by washing and/or wiping; and

at least one temporary layer comprising at least 50% by weight of silica, with respect to the total weight of the temporary layer, wherein the second coating is coated with the temporary layer.

2. The optical article of claim 1 , wherein the temporary layer comprises at least 60% by weight of silica, with respect to the total weight of the temporary layer.

3. The optical article of claim 2 , wherein the temporary layer comprises at least 70% by weight of silica, with respect to the total weight of the temporary layer.

4. The optical article of claim 1 , wherein the temporary layer is the external layer of the optical article, in contact with the air.

5. The optical article of claim 1 , wherein the precursor coating for the antifog coating has a thickness ranging from 3 to 100 nm.

6. The optical article of claim 1 , wherein the compound A is an organosilane and the group capable of establishing a covalent bond with a silanol group is a silicon atom carrying at least one hydrolyzable group.

7. The optical article of claim 6 , wherein the organosilane compound is a compound of formula:

R 1 Y m Si(X) 3-m   (I)

wherein:

each Y group is independently a monovalent organic group bonded to the silicon via a carbon atom;

each X group is independently a hydrolyzable group or hydroxyl group;

R 1 is a group comprising a polyoxyalkylene functional group; and

m is an integer equal to 0, 1 or 2.

8. The optical article of claim 1 , wherein the temporary layer comprises from 1% to 10% by weight of alumina, with respect to the total weight of the temporary layer.

9. The optical article of claim 1 , wherein the temporary layer consists of a layer of silica.

10. The optical article of claim 1 , wherein the temporary layer has a thickness ranging from 5 to 200 nm.

11. The optical article of claim 1 , wherein the second coating that is a precursor to an antifog coating has a surface energy of greater than or equal to 15 mJ/m 2 .

12. The optical article of claim 1 , wherein the coating comprising silanol groups at its surface is an antireflective coating or a silica-based layer deposited on an abrasion-resistant coating.

13. The optical article of claim 1 , further defined as an optical lens.

14. The optical article of claim 13 , wherein the optical lens is an ophthalmic lens.

15. The optical article of claim 1 , wherein the second coating is coated with only one temporary layer comprising at least 50% by weight of silica, with respect to the total weight of the temporary layer.

16. The optical article of claim 1 , wherein the second coating is coated with two midentical or different temporary layers which adhere to one another, each temporary layer comprising at least 50% by weight of silica, with respect to the total weight of the temporary layer.

17. A process for edging an optical article of claim 1 , comprising:

attaching the optical article to a holding device with an adhesive pad which adheres to the surface of the optical article;

mounting the holding device, to which the optical article adheres via the adhesive pad, in an edging device;

edging the optical article by machining the periphery of the optical article; and

after recovering the optical article, removing the temporary layer.

18. The process of claim 17 , wherein the thickness of the precursor coating for the antifog coating, after the removal of the temporary layer, is less than or equal to 5 nm.

19. A process for the preparation of an optical article of claim 1 , comprising:

providing a substrate, at least one of the main surfaces of which is coated with a first coating comprising, at its surface, silanol groups;

depositing on the first coating, a second coating that is in direct contact with the first coating comprising at least one compound A having a polyoxyalkylene group and at least one group capable of establishing a covalent bond with a silanol group, wherein the second coating is further defined as precursor for an antifog coating and comprises an internal part, in which compound A is grafted to the first coating, and an external part that can be removed by washing and/or wiping; and

depositing on the second coating, at least one temporary layer comprising at least 50% by weight of silica, with respect to the total weight of the temporary layer, wherein the second coating is coated with the temporary layer.

20. The method of claim 19 , wherein at least one or both of the second coating and the temporary coating are deposited by vacuum deposition.