Optical article comprising a hard coat, and production method

1. A sol-gel composition forming upon cure a coating for (meth)acrylic polymer-based substrates, the sol-gel composition comprising:

(i) a hard coat solution comprising, by weight relative to its total weight:

130 to 230 parts of a silane hydrolysate that is a hydrolysate of an epoxysilane of formula (V):

wherein:

R 1 is an alkyl group with 1 to 6 carbon atoms,

R 2 is a methyl group or a hydrogen atom,

a is a whole number from 1 to 6, and

b is 0, 1 or 2,

30 to 800 parts of colloid particles of inorganic oxide, and

5 to 20 parts of an aluminum chelate that is a compound formed by reacting an aluminum alcoholate or acylate with at least one nitrogen-and sulphur-free sequestrating agent containing oxygen as the coordinating atom; and

(ii) an adhesion promoter comprising a dendritic polymer having hydroxyl and alkoxysilane groups at terminal ends thereof,

wherein:

the dendritic polymer is a hyperbranched polymer or a dendrimer having:

a degree of functionality in hydroxyl and alkoxysilane of from 5 to 60,

a number average molar mass Mn ranging from 1000 to 15000g/mol, and

a functionalization ratio hydroxyl/alkoxysilane ranging from 0.4 to 2.5;

a content of the adhesion promoter is from 1 to 15% by weight, relative to a total weight of the sol-gel composition; and

the coating for (meth)acrylic polymer-based substrates is an ophthalmic coating.

2. The sol-gel composition of claim 1 , wherein said alkoxysilane groups at terminal ends of the dendritic polymer are obtained by grafting on the dendritic polymers with a coupling agent comprising an alkoxysilane having at least one functional group selected from the group consisting of isocyanate, carboxylic acid and carboxylic acid derivatives, and mixtures thereof.

3. The sol-gel composition of claim 1 , comprising, by weight relative to its total weight:

20 to 150 parts of a silane hydrolysate having formula (I):

wherein:

t 1 and t 2 are groups which will each react to give a OH group on hydrolysis of the silane of formula (I),

Z 1 and Z 2 are organic groups bonded to the silicon atom by a Si—C bond which do not contain a group capable of reacting with the hydrolyzed silanes present in the composition; and

optionally a catalyst, colloidal particles, or both.

4. The sol-gel composition of claim 1 , comprising from 2 to 10% by weight of said adhesion promoter relative to the total weight of the sol-gel composition.

5. An optical article having at least one surface comprising a coating obtained by directly depositing the sol-gel composition of claim 1 on substrate, then curing said sol-gel composition.

6. The optical article of claim 5 , wherein the substrate is a (meth)acrylic substrate with a refractive index ranging from 1.55 to 1.65.

7. A process of preparation of an article as defined in claim 5 , comprising:

preparing the hard coat solution;

preparing the adhesion promoter;

mixing the hard coat solution with the adhesion promoter so as to obtain the sol-gel composition;

coating the substrate with the sol-gel composition; and

curing the sol-gel composition.

8. The process of claim 7 , wherein the preparation of the adhesion promoter comprises the successive following steps:

mixing at least one dendritic polymer having hydroxyl groups at terminal ends thereof in a solvent so as to obtain a mixture;

adding under stirring, to the above mixture, a coupling agent selected from alkoxysilanes;

optionally, adding to the mixture a catalyst; and

obtaining the adhesion promoter by precipitation and/or extraction.

9. The sol-gel composition of claim 4 , comprising from 5 to 8% by weight of said adhesion promoter relative to the total weight of the sol-gel composition.

10. The sol-gel composition of claim 4 , comprising 5% by weight of said adhesion promoter relative to the total weight of the sol-gel composition.

11. The sol-gel composition of claim 2 , wherein the coupling agent comprises an alkoxysilane having at least one functional group which is a carboxylic acid derivative selected from the group consisting of a carboxylic chloride, a carboxylic bromide and a carboxylic anhydride.

12. The sol-gel composition of claim 1 , wherein the dendritic polymer is a hyperbranched polymer or a dendrimer having a degree of functionality in hydroxyl and alkoxysilane of from 10 to 32.

13. The sol-gel composition of claim 1 , wherein the dendritic polymer is a hyperbranched polymer or a dendrimer having a degree of functionality in hydroxyl and alkoxysilane of from 15 to 20.

14. The sol-gel composition of claim 1 , wherein the dendritic polymer has a number average molar mass ranging from 2000 to 12000g/mol.

15. The sol-gel composition of claim 1 , wherein the dendritic polymer has a number average molar mass ranging from 3000 to 5000g/mol.

16. The sol-gel composition of claim 1 , wherein the dendritic polymer has a functionalization ratio hydroxyl/alkoxysilane ranging from 0.65 to 1.5.

17. The optical article of claim 5 , further defined as an ophthalmic article.

18. The optical article of claim 5 , wherein the substrate is a (meth)acrylic substrate.

19. The sol-gel composition of claim 1 , wherein the dendritic polymer has a functionalization ratio hydroxyl/alkoxysilane ranging from 0.95 to 1.05.

20. The sol-gel composition of claim 1 , wherein the dendritic polymer is a hyperbranched polymer or a dendrimer having a degree of functionality in hydroxyl and alkoxysilane of 16.