Substrate with a photocatalytic coating

• US 20040180220A1
• Filed: 04/30/2004
• Published: 09/16/2004
• Est. Priority Date: 05/16/2001
• Status: Active Grant

• Current Assignee: Saint-Gobain Glass France (Compagnie De Saint-Gobain)
• Original Assignee: Saint-Gobain Glass France (Compagnie De Saint-Gobain)
• Inventors: Rondet, Mauricette, Gueneau, Lethicia, Garrec, Ronan, Petit, Jean-Pierre, Denoyelle, Alain, Wouters, Yves
• Granted Patent: US 7,387,839 B2
• Time in Patent Office: Days
• US Class Current: 428/446
• CPC Class Codes: C03C 17/007 containing a dispersed phase, e.g. particles, fibres or flakes, in a continuous phase
• CPC Class Codes: C03C 2217/45 Inorganic continuous phases
• CPC Class Codes: C03C 2217/477 Titanium oxide
• CPC Class Codes: C03C 2217/71 Photocatalytic coatings
• CPC Class Codes: C23C 18/1216 Metal oxides C23C18/1212 takes precedence
• CPC Class Codes: C23C 18/1254 Sol or sol-gel processing
• CPC Class Codes: C23C 18/127 Preformed particles
• CPC Class Codes: C23C 18/1279 performed under reactive atmosphere, e.g. oxidising or reducing atmospheres
• CPC Class Codes: Y02T 50/60 Efficient propulsion technologies, e.g. for aircraft

Abstract

The subject of the invention is a substrate provided on at least part of at least one of its faces with a coating having photocatalytic properties, containing photocatalytic titanium oxide, especially crystallized in the anatase form, in an essentially mineral binder comprising at least one semiconducting metal oxide.

The subject of the invention is also a process for obtaining said substrate, especially by thermal decomposition of precursors or by a vacuum deposition technique.

Claims

1. A substrate provided on at least part of at least one of its faces with a coating having photocatalytic properties, containing photocatalytic titanium oxide, especially crystallized in the anatase form, in an essentially mineral binder comprising at least one semiconducting metal oxide.

2. The substrate as claimed in claim 1, characterized in that at least part of the photocatalytic titanium oxide is incorporated into the coating in the form of preformed particles, especially of nanometric size.

3. The substrate as claimed in one of the preceding claims, characterized in that at least part of the photocatalytic titanium oxide is formed during formation of the coating, especially by thermal decomposition of precursors.

4. The substrate as claimed in one of the preceding claims, characterized in that the or at least one of the semiconducting metal oxides of the binder has an electrical resistivity of less than or equal to 10⁸ ohm.cm.

5. The substrate as claimed in one of the preceding claims, characterized in that the or at least one of the semiconducting metal oxides of the binder is catalytic with respect to the reduction of oxygen.

6. The substrate as claimed in one of the preceding claims, characterized in that the or at least one of the semiconducting metal oxides of the binder is doped, especially with a metal or a halogen.

7. The substrate as claimed in one of the preceding claims, characterized in that the or at least one of the semiconducting metal oxides of the binder:

has the lowest energy level of its conduction band, which is less than or equal to the lowest energy level of the conduction band of the photocatalytic titanium oxide;

is close to the most probable electron energy level of the oxygen in the O₂/H₂O₂ and/or O₂/H₂O redox couple.

8. The substrate as claimed in one of the preceding claims, characterized in that the or at least one of the semiconducting metal oxides of the binder is based on titanium oxide, tin oxide, antimony oxide, zinc oxide, tungsten oxide, cobalt oxide, nickel oxide or nickel and cobalt mixed oxide, possibly doped, or a mixed oxide chosen from manganites and cobaltites.

9. The substrate as claimed in one of claims 1 to 6 characterized in that the or at least one of the semiconducting metal oxides of the binder:

has the lowest energy level of its conduction band, which is greater than the lowest level of the conduction band of the photocatalytic titanium oxide;

has electron states in the band gap, especially those associated with structural defects and/or pendant bonds.

10. The substrate as claimed in one of the preceding claims, characterized in that the or at least one of the semiconducting metal oxides of the binder is based on zirconium oxide or aluminum oxide, these possibly being doped.

11. The substrate as claimed in one of the preceding claims, characterized in that the binder also includes an electrically insulating compound, especially a silicon derivative such as silicon oxide, silicon oxynitride, silicon oxycarbide or silicon nitride.

12. The substrate as claimed in one of the preceding claims, characterized in that the content of semiconducting metal oxide(s) in the binder is at least 25% by weight, especially at least 50% and up to 100% by weight.

13. The substrate as claimed in one of the preceding claims, characterized in that the ratio by weight of the photocatalytic titanium oxide to the binder R_TiO2/binder varies between 10/90 and 60/40, especially between 10/90 and 50/50.

14. The substrate as claimed in one of the preceding claims, characterized in that the amount of titanium oxide present in the coating is from 5 to 100 μ

g/cm², especially from 10 to 50 μ

g/cm².

15. The substrate as claimed in one of the preceding claims, characterized in that the binder is a mixture of zirconium oxide, or of titanium oxide with silicon oxide.

16. The substrate as claimed in one of the preceding claims, characterized in that the photocatalytic activity of the coating is at least 2 nm/h/(μ

g/cm²) especially at least 5 or 10 or 20 nm/h/(μ

g/cm²), relative to the total amount of titanium oxide of said coating.

17. The substrate as claimed in one of the preceding claims, characterized in that at least one thin layer having an optical function, thermal function by acting as a barrier to the migration of species diffusing from the substrate is deposited between said substrate and the coating having photocatalytic properties.

18. The substrate as claimed in one of the preceding claims, characterized in that it is an architectural material, especially glazing, a roofing, cladding, floor or false-ceiling material, or a material intended to equip means of locomotion, especially glazing for an automobile, train, airplane, or boat, or a material intended for domestic electrical appliances, especially for oven walls or glazed walls of a refrigerator/freezer.

19. The substrate as claimed in one of the preceding claims, characterized in that it is based on a transparent material of the glass or polymer type, or based on a ceramic or based on tile or brick or based on wood, metal, cement, stone or render or based on fibrous materials of the insulating glass wool type or an assembly of glass reinforcing yarns.

20. A process for obtaining the substrate as claimed in one of the preceding claims, characterized in that the coating having photocatalytic properties is deposited by a technique involving the thermal decomposition of at least one organometallic precursor or metal halide, of the sol-gel, powder pyrolysis, liquid pyrolysis or chemical vapor deposition type.

21. The process as claimed in claim 20 characterized in that, in order to facilitate the incorporation of halogen into the coating, when it is obtained from at least one precursor of the metal halide type, a heat treatment is carried out on said coating in an atmosphere which is substoichiometric in terms of oxygen.

22. The process for obtaining the substrate as claimed in one of claims 1 to 19 characterized in that the coating having photocatalytic properties is deposited by a vacuum deposition technique, especially by sputtering.