Process for the manufacturing of an optical article and optical article

1. A process for the manufacturing of an optical article comprising:

a) providing an uncoated or coated substrate,

b) forming on at least one face of said substrate a multilayered coating,

c) forming on an outermost layer of said multilayered coating, a layer-by-layer (LbL) coating exposed to environment, said LbL coating comprising at least two bilayers, each bilayer being formed successively by:

i) applying a first layer composition comprising at least one compound A having a first electrical charge;

ii) applying, directly onto the first layer resulting from i), a second layer composition comprising at least one compound B having a second electrical charge, said second electrical charge being opposite to said first electrical charge;

iii) repeating at least once steps i) and ii),

with the provisos that:

each of compounds A and B is independently a polysaccharide polymer or colloid of metal oxide, with the proviso that at least one of the compounds A and B is a polysaccharide polymer;

each of said compounds A and B is positively or negatively charged respectively; and

d) crosslinking the first and second layers of said bilayers of the LbL coating by treatment with an aqueous composition comprising at least from 0.2 to 5 weight % of the total weight of said composition of tetrakis(2-hydroxyethyl) orthosilicate (THEOS) as a crosslinking agent to induce chemical linkages between compounds A and B.

2. The process of claim 1 , wherein at least one compound A or B is a colloid of metal oxide further defined as comprising TiO 2 , and ZrO 2 , or silicon oxide.

3. The process of claim 2 , wherein said colloid of metal oxide is further defined as silicon oxide comprising surface amino- functionalized SiO 2 nanoparticles and/or surface negatively charged SiO 2 nanoparticles.

4. The process of claim 1 , wherein said polysaccharide polymers comprise at least one polysaccharide comprising a glucosamine unit or polysaccharide comprising a carboxylic acid group.

5. The process of claim 4 , wherein said polysaccharide comprises a glucosamine unit and is further defined chitosan or poly(1,3-β-D-glucosamine-alt-1,4-β-D-glucuronic acid).

6. The process of claim 4 , wherein said polysaccharide comprises a carboxylic acid group and is further defined as comprising carboxyalkylcellulose, alginate, and/or xanthan.

7. The process of claim 6 , the polysaccharide is a carboxyalkylcellulose further defined as carboxymethyl cellulose, carboxyethyl cellulose, or carboxypropyl cellulose.

8. The process of claim 1 , wherein each bilayer of said LbL coating comprises:

a first layer of chitosan as compound A and a second layer of carboxymethyl cellulose as compound B; or

a first layer of aminopropyl-functionalized SiO 2 nanoparticles as compound A and a second layer of carboxymethyl cellulose as compound B; or

a first layer of chitosan as compound A and a second layer of SiO 2 as compound B.

9. The process of claim 1 , wherein the amount of THEOS in said crosslinking aqueous solvent-based composition ranges from 0.5 to 1 weight % of the total weight of said composition.

10. The process of claim 1 , wherein said crosslinking step d) is carried out by thermal annealing at a temperature ranging from 30° C. to 120° C. for a period of 0.5 to 12 hours.

11. The process of claim 10 , wherein said crosslinking step d) is carried out by thermal annealing at a temperature ranging from 30° C. to 120° C. for a period of 1 to 3 hours.

12. The process of claim 11 , wherein said crosslinking step d) is carried out by thermal annealing at a temperature ranging from 50 to 70° C.

13. The process of claim 10 , wherein said crosslinking step d) is carried out by thermal annealing at a temperature ranging from 40° C. to 100° C.

14. The process of claim 1 , wherein the LbL coating is at least partially dried before the crosslinking step d) is carried out.

15. The process of claim 1 , wherein said multilayered coating is an antireflecting coating further comprising a stack of low refractive index layers (LI layers) having a refractive index n ≤1.55 and high refractive index layer (HI layers) having a refractive index n′ >1.55, said multilayered coating being deposited onto the substrate through a vacuum evaporation process.

16. The process of claim 15 , wherein:

the LI layers are made of SiO 2 , SiO x , with 1≤x<2, MgF 2 , ZrF 4 , AlF 3 , chiolote (Na 5 Al 3 F 14 ), cryolite (Na 3 AlF 6 ), mixtures of SiO 2 and/or SiO x with at most 10% by weight of A 1 2 O 3 , and mixtures thereof; and

the HI layers are made of ZrO 2 , TiO 2 , Ta 2 O 5 , Na 2 O 5 , Pr 2 O 3 , PrTiO 3 , La 2 O 3 , Dy 2 O 5 , Nb 2 O 5 , Y 2 O 3 , mixtures thereof, and mixtures of these oxides with silica and/or alumina.

17. An optical article formed by the process of claim 1 .

18. The optical article of claim 17 , wherein each bilayer of said LbL coating comprises a first layer of chitosan as compound A and a second layer of carboxymethyl cellulose as compound B.

19. The optical article of claim 17 , wherein each bilayer of said LbL coating comprises a first layer of aminopropyl- functionalized SiO 2 nanoparticles as compound A and a second layer of carboxymethyl cellulose as compound B.

20. The optical article of claim 17 , wherein each bilayer of said LbL coating comprises a first layer of chitosan as compound A and a second layer of SiO 2 as compound B.

21. The optical article of claim 17 , wherein the amount of THEOS in said crosslinking aqueous solvent-based composition ranges from 0.5 to 1.0 weight % of the total weight of said composition.