ANTI-REFLECTIVE COATINGS FOR OPTICALLY TRANSPARENT SUBSTRATES

• US 20100313950A1
• Filed: 06/08/2010
• Published: 12/16/2010
• Est. Priority Date: 06/10/2009
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Dankers, Lea, Mukhopadhyay, Sudip, Pandey, Yamini
• Granted Patent: US 8,557,877 B2
• Time in Patent Office: Days
• US Class Current: 136/256
• CPC Class Codes: C03C 17/30 with silicon-containing compounds
• CPC Class Codes: C03C 2217/732 made of a single layer
• CPC Class Codes: C09D 5/00 Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced electrically insulating plastics, resins or waxes H01B3/30; Filling pastes
• CPC Class Codes: G02B 1/111 using layers comprising organic materials
• CPC Class Codes: H01L 31/02161 for devices characterised by at least one potential jump barrier or surface barrier
• CPC Class Codes: H01L 31/02168 the coatings being antireflective or having enhancing optical properties for the solar cells
• CPC Class Codes: H01L 31/042 PV modules or arrays of single PV cells supporting structures for PV modules H02S20/00
• CPC Class Codes: Y02E 10/50 Photovoltaic [PV] energy
• CPC Class Codes: Y02E 10/52 PV systems with concentrators
• CPC Class Codes: Y10T 428/254 Polymeric or resinous material
• CPC Class Codes: Y10T 428/31504 Composite [nonstructural laminate]
• CPC Class Codes: Y10T 428/31663 As siloxane, silicone or silane

Abstract

Anti-reflective coatings and coating solutions, optically transparent elements and improved processes for preparing AR coatings and coating solutions are described. The anti-reflective coatings are formed from at least two different alkoxy silane materials in a base catalyzed reaction.

Claims

1. An optically transparent element comprising:

an optically transparent substrate; and

an anti-reflective coating disposed on at least one surface of the optically transparent substrate, the anti-reflective coating comprising a polymer, the polymer comprising;

at least one tetraalkoxy silane residue; and

at least a second alkoxy silane residue selected from the group consisting of trialkoxy silanes, dialkoxy silanes, monoalkoxy silanes, and combinations thereof, wherein the polymer comprises at least 50 mole percent of the at least one tetraalkoxy silane residue based on the total moles of polymer and the coating comprises polymer particles having an average size of no more than 100 nm.

2. The optically transparent element of claim 1 wherein the at least one alkoxy silane residue is tetraethoxy silane.

3. The optically transparent element of claim 1 wherein the second alkoxy silane residue is selected from the group consisting of methyltriethoxy silane and vinyltriethoxy silane.

4. The optically transparent element of claim 1 wherein the at least one tetraalkoxy silane residue is tetraethoxy silane and the second alkoxy silane is methyltriethoxy silane.

6. The optically transparent element of claim 1 wherein the polymer consists essentially of tetraethoxy silane residues and methyltriethoxy silane residues and has an average particle size of between 15 and 100 nm.

7. The optically transparent element of claim 1 wherein the polymer further comprises a metal alkoxide residue.

8. The optically transparent element of claim 1 wherein the polymer further comprises a titanium isopropoxide residue.

9. The optically transparent element of claim 1 comprising at least about 20 mole percent of the second alkoxy silane residue.

10. The optically transparent element of claim 1 comprising between about 20 mole percent and 40 mole percent of the second alkoxy silane residue.

5. The optically transparent element of claim 5 further comprising a vinyltriethoxy silane residue.

11. A photovoltaic module comprising:

At least one semiconductor layer;

an optically transparent layer disposed over the at least one semiconductor layer; and

an anti-reflective coating disposed on at least one surface of the optically transparent substrate, the anti-reflective coating comprising a polymer, the polymer comprising;

at least one tetraalkoxy silane residue; and

at least a second alkoxy silane residue selected from the group consisting of trialkoxy silanes, dialkoxy silanes, monoalkoxy silanes, and combinations thereof, wherein the polymer comprises at least 50 mole percent of the at least one tetraalkoxy silane residue based on the total moles of polymer and the coating comprises polymer particles having an average size of no more than 100 nm.

12. The photovoltaic module of claim 11 wherein the at least one tetraalkoxy silane is tetraethoxy silane and the second alkoxy silane residue is selected from the group consisting of, methyltriethoxy silane, vinyltriethoxy silane and combinations thereof.

13. A method of producing a coating solution, comprising:

combining at least a first tetraalkoxy silane material, a second alkoxy silane material, a base catalyst and a solvent to form a coating, wherein the second alkoxy silane material is selected from the group consisting of trialkoxy silanes, dialkoxy silanes, monoalkoxy silanes and combinations thereof;

maintaining the pH of the coating solution for a sufficient period of time at a sufficient temperature to form polymer particles having an average particle size between about 15 nm and about 100 nm; and

reducing the pH of the coating solution to less than about 5.0.

14. The method of claim 13, wherein the base catalyst comprises at least one quaternary ammonium.

15. The method of claim 13, wherein the base catalyst comprises tetrabutylammonium hydroxide, tetramethylammonium hydroxide or a combination thereof.

16. The method of claim 13 wherein the coating solution is maintained at between about 35°

C. and about 70°

C. for between about 1 and about 5 hours prior to reducing the pH.

17. The method of claim 13 wherein the solvent comprises water.

18. The method of claim 13 wherein the pH is reduced to no more than 2.0.

19. The method of claim 13 further comprising the step of storing the coating solution for at least about 24 hours.

20. The method of claim 19 further comprising the step of freezing the coating solution.

21. A method of forming an optically transparent element comprising:

dispensing the coating solution of claim 19 onto an optically transparent substrate; and

curing the coating solution to form an anti-reflective coating on the optically transparent substrate.

22. The method of claim 21 wherein the coating solution is dispensed by spraying.

23. The method of claim 21 wherein prior to dispensing, the coating solution is changed from a frozen state to a liquid state.

24. An optically transparent element formed by the method of claim 21.

25. An anti-reflective coating solution comprising:

a polymer comprising;

at least one tetraalkoxy silane residue; and

at least a second alkoxy silane residue selected from the group consisting of trialkoxy silanes, dialkoxy silanes, monoalkoxy silanes, and combinations thereof, wherein the polymer comprises at least 50 mole percent of the at least one tetraalkoxy silane residue based on the total moles of polymer and the coating comprises polymer particles having an average size of no more than 100 nm;

a solvent, wherein the coating solution has a polymer particle concentration of up to about 25 wt % and a viscosity of no more than 2.0 cP, and

wherein the coating solution has a viscosity of no more than 2.0 cP and a pH of no more than 5.0 for at least 24 hours at 25°

C.

26. The anti-reflective coating solution of claim 25 wherein the polymer consists essentially of tetraethoxy silane residues and methyltriethoxy silane residues.