Novel hybrid sol for the production of abrasion-resistant sio2 antireflection coatings

• US 20040248995A1
• Filed: 03/19/2004
• Published: 12/09/2004
• Est. Priority Date: 09/21/2001
• Status: Active Grant

• Current Assignee: Merck Patentgesellschaft
• Original Assignee: Merck Patentgesellschaft
• Inventors: Hofmann, Thomas, Glaubitt, Walther, Gombert, Andreas, Kursawe, Monika
• Granted Patent: US 7,241,505 B2
• Time in Patent Office: Days
• US Class Current: 516/34
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C01B 33/145 Preparation of hydroorganosols, organosols or dispersions in an organic medium
• CPC Class Codes: C03C 17/001 General methods for coating; Devices therefor
• CPC Class Codes: C03C 17/007 containing a dispersed phase, e.g. particles, fibres or flakes, in a continuous phase
• CPC Class Codes: C03C 17/25 by deposition from the liquid phase
• CPC Class Codes: C03C 2217/213 SiO2
• CPC Class Codes: C03C 2217/425 consisting of a porous layer
• CPC Class Codes: C03C 2218/113 by sol-gel processes
• CPC Class Codes: C08L 2666/54 Inorganic substances
• CPC Class Codes: C09D 183/02 Polysilicates
• CPC Class Codes: Y10T 428/31612 As silicone, silane or siloxane

Abstract

Hybrid sol comprising [SiO_x(OH)_y]_n particles, where 0<y<4 and 0<x<2, which consist of a mixture of a first fraction of particles having a particle size of 4-15 nm and a second fraction of particles having a mean particle size of 15-60 nm, water and a solvent; obtainable by hydrolytic polycondensation of tetraalkoxysilanes in an aqueous, solvent-containing medium with addition of a monodisperse silicon oxide hydroxide sol having a mean particle size of 15-60 nm and a maximum standard deviation of 20%, and the preparation and use thereof.

Claims

1. Hybrid sol comprising

[SiO_x(OH)_y]_n particles, where 0<

y<

4 and 0<

x<

2, which consist of a mixture of a first fraction of particles having a particle size of 4-15 nm and a second fraction of particles having a mean particle size of 20-60 nm,

water and a solvent, obtainable by

hydrolytic polycondensation of tetraalkoxysilanes in an aqueous, solvent-containing medium, giving silicon oxide hydroxide particles having a particle size of 4-15 nm, with addition of a monodisperse silicon oxide hydroxide sol having a mean particle size of 20-60 nm and a maximum standard deviation of 20%.

2. Hybrid sol according to claim 1, where the hydrolytic polycondensation is carried out in the presence of a basic catalyst.

3. Hybrid sol according to claim 1, where a stabiliser is subsequently added.

4. Hybrid sol according to claim 1, where the monodisperse silicon oxide hydroxide sol is obtainable by addition of a tetraalkoxysilane to an aqueous-alcoholic ammoniacal hydrolysis mixture, with formation of primary silicon oxide hydroxide particles, and continuous addition of further tetraalkoxysilane to this mixture in such a way that essentially no further particles are formed.

5. Hybrid sol according to claim 4, where the monodisperse silicon oxide hydroxide sol is obtainable at a temperature of 35-80°

C.

6. Hybrid sol according to claim 4, where alcohol and ammonia are removed from the monodisperse silicon oxide hydroxide sol before addition to the aqueous, solvent- and tetraalkoxysilane-containing hydrolysis mixture.

7. Hybrid sol according to claim 1, where the weight ratio between the first particle fraction and the second particle fraction is from 25:

1 to 1;

5.

8. Hybrid sol according to claim 1, where the concentration of the [SiO_x(OH)_y]_n particles is 0.3-4% by weight.

9. Hybrid sol according to claim 1, where the solvent is a lower aliphatic alcohol.

10. Hybrid sol according to claim 9, where the lower aliphatic alcohol is methanol, ethanol, i-propanol or n-propanol.

11. Hybrid sol according to claim 3, where the stabiliser is a glycol ether or an ether of another alcohol or a mixture of these ethers.

12. Hybrid sol according to claim 1, comprising 0.3-4% by weight of [SiO_x(OH)_y]_n particles, 2-50% by weight of water and 2-97% by weight of solvent.

13. Hybrid sol according to claim 1, comprising 1-2% by weight of [SiO_x(OH)_y]_n particles, 10-35% by weight of water, 15-30% by weight of solvent and 40-70% by weight of stabiliser.

14. Process for the preparation of a hybrid sol according to claim 1 by hydrolytic polycondensation of a tetraalkoxysilane in an aqueous, solvent-containing medium, giving a hydrolysis mixture comprising silicon oxide hydroxide particles having a particle size of 4-15 nm, and addition of a monodisperse silicon oxide hydroxide sol having a mean particle size of 20-60 nm and a maximum standard deviation of 20% at a time at least 5 minutes after addition of the tetraalkoxysilane to the aqueous, solvent-containing medium.

15. Process according to claim 14, where the hydrolytic polycondensation is carried out at a temperature of from 5 to 90°

C.

16. Process according to claim 14, where the hybrid sol is mixed vigorously for a period of from 1 minute to 48 hours at temperatures of from 10 to 40°

C. after addition of the monodisperse silicon oxide hydroxide sol.

17. Process according to claim 14, where the hydrolysis mixture comprising silicon oxide hydroxide particles having a particle size of 4-15 nm is prepared with addition of a basic catalyst and has a pH of ≧

7.

18. Process according to 17claim 14, where a stabiliser is subsequently added.

19. Process according to claim 18, where the stabiliser is a glycol ether or an ether of another alcohol or a mixture of these ethers.

20. Process according to claim 14, where the addition of the monodisperse silicon oxide hydroxide sol to the hydrolysis mixture is carried out at a time from at least 5 minutes to at most 48 hours after addition of the tetraalkoxysilane to the aqueous, solvent-containing medium.

21. Process according to claim 20 where the addition is carried out after from 20 to 180 minutes.

22. Use of the hybrid sol according to claim 1, for the deposition of abrasion-resistant, optically transparent, porous SiO₂ layers having a refractive index of from 1.20 to 1.40 on glass.

23. Glass having a porous antireflection layer of silicon dioxide having a refractive index of from 1.20 to 1.40, deposited from a hybrid sol according to claim 1.