Substrate, in particular glass substrate, supporting a photocatalytic layer coated with a protective thin layer

• US 20070148064A1
• Filed: 10/22/2004
• Published: 06/28/2007
• Est. Priority Date: 10/23/2003
• Status: Active Grant

• Current Assignee: Saint-Gobain Glass France (Compagnie De Saint-Gobain)
• Original Assignee: Saint-Gobain Glass France (Compagnie De Saint-Gobain)
• Inventors: LABROUSSE, Laurent
• Granted Patent: US 7,884,047 B2
• Time in Patent Office: Days
• US Class Current: 422/211
• CPC Class Codes: C03C 17/3417 all coatings being oxide coatings
• CPC Class Codes: C03C 17/3423 at least one of the coatings comprising a suboxide
• CPC Class Codes: C03C 17/3435 comprising a nitride, oxynitride, boronitride or carbonitride
• CPC Class Codes: C03C 17/3441 comprising carbon, a carbide or oxycarbide
• CPC Class Codes: C03C 2217/71 Photocatalytic coatings
• CPC Class Codes: Y10T 428/29 Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
• CPC Class Codes: Y10T 428/2991 Coated
• CPC Class Codes: Y10T 428/2993 Silicic or refractory material containing [e.g., tungsten oxide, glass, cement, etc.]

Abstract

The invention relates to a structure, comprising a substrate supporting a layer with a photocatalytic and anti-soiling property, said layer being based on titanium dioxide (TiO₂), on at least part of the surface thereof. Said structure is characterised in that the photocatalytic layer is coated with a non-porous thin layer, containing silicon and oxygen and having a coating capacity, providing a chemical and mechanical protection to the underlying photocatalytic layer, whilst maintaining the TiO₂ photocatalytic activity.

Claims

1. A structure comprising a substrate bearing, on at least part of its surface, a photocatalytic antisoiling layer comprising titanium dioxide (TiO₂), wherein said photocatalytic antisoiling layer is coated with a thin nonporous layer comprising silicon and oxygen and having a covering power, wherein said thin nonporous layer mechanically and chemically protects the underlying photocatalytic layer, while maintaining the photocatalytic activity of the titanium dioxide (TiO₂).

2. The structure of claim 1, wherein said thin nonporous layer comprising silicon and oxygen is present in the form of a continuous film.

3. The structure of claim 1, wherein said thin layer comprising silicon and oxygen is present in the form of a film that conforms to the surface asperities of the underlying photocatalytic antisoiling layer.

4. The structure of claim 1, wherein the thin nonporous layer comprising silicon and oxygen is a layer of at least one silicon-oxygen compound selected from the group consisting of SiO₂, SiOC, SiON, SiO_x, wherein x<

2, and SiOCH.

5. The structure of claim 1, wherein the thin nonporous layer comprising silicon and oxygen is a layer of at least one silicon-oxygen compound further comprising at least one compound selected from the group consisting of Al₂O₃ and ZrO₂.

6. The structure as claimed in claim 5, wherein the Al/Si, the Zr/Si or the Al/Si and Zr/Si (Al and/or Zr)/Si atomic ratio does not exceed 1.

7. The structure of claim 5, wherein the structure comprises Al₂O₃ and wherein the Al/Si ratio is from 0.03 to 0.5.

8. The structure of claim 5, wherein the structure comprises ZrO₂ and wherein the Zr/Si ratio is from 0.05 to 0.4.

9. The structure of claim 1, wherein the thin nonporous layer comprising silicon and oxygen has a thickness of at most 15 nm.

10. The structure as claimed in claim 1, wherein the photocatalytic antisoiling layer consists of TiO₂ alone or of TiO₂ doped with at least one dopant chosen especially selected from the group consisting of N pentavalent cations of Nb, pentavalent cations of Ta pentavalent cations of V, Fe, and Zr.

11. The structure of claim 1, wherein the photocatalytic antisoiling layer has been deposited by

a sol-gel method,

or by a pyrolysis method or by room-temperature vacuum sputtering, using a metal or TiO_x target, wherein x<

2, and in an oxidizing atmosphere, or using a TiO₂ target in an inert atmosphere, the TiO₂ produced by the sputtering then optionally being subjected to a heat treatment so as to be in the crystallized state in a photocatalytically active form.

12. The structure of claim 1, wherein the thin nonporous layer comprising silicon and oxygen has been deposited by room-temperature vacuum sputtering using a target of Al (8 at %)-doped Si, in an Ar/O₂ atmosphere, at a pressure of 0.2 Pa.

13. The structure of claim 1, further comprising, immediately below the photocatalytic antisoiling layer, an underlayer having a crystallographic structure for assisting in the crystallization, by heteroepitaxial growth, in the anatase form of the photocatalytic antisoiling upper layer.

14. The structure of claim 1, 1 wherein the substrate comprises a sheet,

whether plane or having curved faces, wherein the sheet comprises at least one material selected from the group consisting of monolithic glass, laminated glass, glass-ceramic, and a hard thermoplastic, or glass fibers, or glass-ceramic fibers,

wherein said sheet or said fibers have, optionally, received at least one other functional layer before application of photocatalytic antisoiling layer or of or have, optionally, received a layer for assisting in the crystallization of the photocatalytic antisoiling layer by heteroepitaxial growth.

15. The structure of claim 14, comprising the at least one other functional layer, wherein the at least one other functional layer is selected from the group consisting of at least one layer having an optical functionality, at least one thermal control layer and at least one conducting layer, and wherein, if the substrate comprises glass or glass-ceramic, the at least one other functional layer acts as a barrier to the migration of alkali metals from the glass or from the glass-ceramic.

16. A process for manufacturing the structure of claim 1, comprising

depositing an optionally doped TiO₂ layer on a substrate made of comprising glass, glass-ceramic, polycarbonate-type hard plastic, of the sheet type, glass fibers, or glass-ceramic fibers,

wherein said optionally doped TiO₂ layer is optionally subjected to a heat treatment in order to give it a photocatalytic property if the photocatalytic property is not provided by the conditions used for depositing the optionally doped TiO₂ layer, and

depositing a thin layer comprising silicon and oxygen on said photocatalytic layer, to form the structure of claim 1.

17. The process of claim 16, wherein the deposition of the TiO₂ layer and the thin layer comprising silicon and oxygen are carried out in succession at room temperature, by vacuum sputtering, in the same chamber, the conditions being the following:

for depositing the TiO₂ layer, supply in AC or DC mode, at a pressure of 1-3 mbar and in an oxygen/inert gas (argon) atmosphere, using a Ti or TiO_x, target, where x=1.5 to 2; and

for depositing the layer comprising silicon and oxygen, supply in AC mode at a pressure of 0.1 to 1.0 Pa and in an Ar/O₂ atmosphere using a target having a high silicon content,

the deposition of the TiO₂ layer being optionally preceded by the deposition of an underlayer for assisting in the crystallization by epitaxial growth in the anatase form of the TiO₂ layer.

18. The process of claim 16, wherein the substrate is a glass or glass-ceramic substrate, wherein, before application of the TiO₂ layer, at least one layer forming a barrier to the migration of alkali metals present in the glass or glass-ceramic substrate is deposited on the substrate, and wherein, optionally, an annealing or toughening operation is carried out after the TiO₂ layer and the thin layer covering the TiO₂ layer have been deposited.

19. The process of claim 18, wherein, after the application of the at least one layer forming a barrier to the migration of alkali metals and before application of the TiO₂ layer, at least one functional layer selected from the group consisting of at least one layer having an optical functionality, at least one thermal control layer, and at least one conducting layer is deposited, wherein said at least one functional layer is advantageously deposited by vacuum sputtering.

20. A single or multiple glazing, comprising, on at least one face respectively, the structure as defined in claim 1.

21. The structure of claim 11, wherein the TiO₂ is subjected to a heat treatment so as to be in the crystallized state in a photocatalytically active form.

22. The structure of claim 11, wherein the room-temperature vacuum sputtering comprises magnetron sputtering.

23. The structure of claim 11, wherein the room-temperature vacuum sputtering comprises ion-beam sputtering.

24. The structure of claim 11, wherein the room-temperature vacuum sputtering comprises magnetron sputtering and ion-beam sputtering.

25. The structure of claim 14, wherein the sheet or the fibers have received at least one other functional layer before application of the photocatalytic antisoiling layer.

26. The structure of claim 14, comprising a layer for assisting in the crystallization of the photocatalytic antisoiling layer by heteroepitaxial growth.

27. The process of claim 16, wherein the TiO₂ layer is doped.

28. The process of claim 17, comprising depositing an underlayer for assisting in the crystallization by epitaxial growth in the anatase form of the TiO₂ layer.

29. The process of claim 18, comprising carrying out an annealing operation, wherein the annealing operation is carried out at a temperature of between 250°

C. and 500°

C.

30. The process of claim 18, comprising carrying out a toughening operation, wherein the toughening operation is carried out at a temperature of at least 600°

C.