Substrate Having a Photocatalytic Coating

• US 20070218264A1
• Filed: 05/10/2005
• Published: 09/20/2007
• Est. Priority Date: 05/10/2004
• Status: Active Grant

• Current Assignee: Saint-Gobain Glass France (Compagnie De Saint-Gobain)
• Original Assignee: Saint-Gobain Glass France (Compagnie De Saint-Gobain)
• Inventors: Mattmann, Eric, Gueneau, Lethicia, Rondet, Mauricette
• Granted Patent: US 8,815,378 B2
• Time in Patent Office: Days
• US Class Current: 428/220
• CPC Class Codes: B32B 3/26 characterised by a particular shape of the outline of the cross-section of a continuous layer; characterised by a layer with cavities or internal voids foam layer B32B5/18; layer of synthetic resin characterised by fillers that create voids or cavities B32B27/205; characterised by an apertured layer
• CPC Class Codes: C03C 17/3417 all coatings being oxide coatings
• CPC Class Codes: C03C 17/3435 comprising a nitride, oxynitride, boronitride or carbonitride
• CPC Class Codes: C03C 2217/71 Photocatalytic coatings
• CPC Class Codes: C03C 2217/734 comprising an alternation of high and low refractive indexes
• CPC Class Codes: G02B 1/04 made of organic materials, e.g. plastics G02B1/08 takes precedence
• CPC Class Codes: G02B 1/11 Anti-reflection coatings
• CPC Class Codes: G02B 1/113 using inorganic layer materials only
• CPC Class Codes: G02B 1/115 Multilayers
• CPC Class Codes: G02F 1/1333 Constructional arrangements; Manufacturing methodsG02F1/135, G02F1/136 take precedence
• CPC Class Codes: G02F 1/133305 Flexible substrates, e.g. plastics, organic film
• CPC Class Codes: Y10T 428/24942 including components having same physical characteristic in differing degree
• CPC Class Codes: Y10T 428/24975 No layer or component greater than 5 mils thick
• CPC Class Codes: Y10T 428/249953 Composite having voids in a component [e.g., porous, cellular, etc.]
• CPC Class Codes: Y10T 428/249956 Void-containing component is inorganic
• CPC Class Codes: Y10T 428/249969 Of silicon-containing material [e.g., glass, etc.]
• CPC Class Codes: Y10T 428/249986 Void-containing component contains also a solid fiber or solid particle

Abstract

The invention relates to a transparent or semi-transparent substrate having, over at least a portion of at least one of its surfaces, a photocatalytic coating based on titanium oxide and characterized in that the coated surface has a luminous reflectance less than that of a non-coated surface of the substrate. The invention also relates to methods for obtaining a substrate of this type and to uses for this substrate

Claims

1. A transparent or semitransparent substrate having, on at least part of at least one of its sides, a photocatalytic coating based on titanium dioxide, wherein the coated side has a light reflectance lower than that of an uncoated side of the substrate.

2. The substrate as claimed in claim 1, wherein at least one coating is inserted between the substrate and the photocatalytic coating in order to reduce the light reflectance.

3. The substrate as claimed in claim 2, wherein the coating inserted between the substrate and the photocatalytic coating is a multilayer stack.

4. The substrate as claimed in claim 3, wherein the coating inserted between the substrate and the photocatalytic coating consisting essentially of thin dielectric layers comprising in succession:

a first high-index layer 1, having a refractive index n₁ of between 1.8 and 2.3 and a geometric thickness e₁ of between 5 and 50 nm,

a second low-index layer 2, having a refractive index n₂ of between 1.35 and 1.65 and a geometric thickness e₂ of between 10 and 60 nm,

a third high-index layer 3, having a refractive index n₃ of between 1.8 and 2.5 and a geometric thickness e₃ of between 40 and 150 nm.

5. The substrate of claim 3, wherein the multilayer stack does not comprise a metal layer.

6. The substrate of claim 1, wherein the coated side has a reflectance lower than or equal to 60% of that of an uncoated side of the substrate.

7. The substrate of claim 2, wherein the coated side has a reflectance lower than or equal to 15% of that of an uncoated side of the substrate.

8. The substrate of claim 1, wherein the coated side has a reflectance lower than the reflectance of an uncoated side of the substrate over the entire 400 800 nm range.

9. The substrate of claim 1, wherein the extent of the thickness range of the photocatalytic coating for which the reflectance of the coated substrate remains lower than the reflectance of the uncoated substrate represents at least 15% of the median value of this range.

10. The substrate of claim 1 wherein the photocatalytic coating has a refractive index lower than 1.8 at 550 nm.

11. The substrate of claim 1, wherein the photocatalytic coating has a refractive index lower than 1.6 at 550 nm.

12. The substrate of claim 1, wherein the photocatalytic coating has an activity under outdoor lighting conditions, expressed as the rate of degradation of stearic acid, which is greater than or equal to 1×

10<sup>−

2</sup> cm<sup>−

1</sup>/min.

13. The substrate of claim 1, wherein the photocatalytic coating has an activity under indoor lighting conditions, expressed as a weight percentage of degraded stearic acid, that is greater than or equal to 15%.

14. The substrate of claim 1, wherein the photocatalytic coating has an activity under indoor lighting conditions, expressed as a weight percentage of degraded stearic acid, that is greater than or equal to 30%.

15. The substrate of claim 1, wherein the photocatalytic coating has a mesoporous structure comprising at least partially crystalline titanium dioxide.

16. The substrate of claim 1, wherein with the exception of titanium dioxide, the mesoporous structure comprising silica (SiO₂).

17. The substrate of claim 15, wherein the at least partially crystalline titanium dioxide is incorporated in the mesoporous structure in the form of perfectly discernible particles.

18. The substrate of claim 16, wherein the Ti/Si atomic ratio is between 0.6 and 1.2.

19. The plastic substrate of claim 1, wherein a scratch-resistant or abrasion-resistant coating is inserted between the substrate and the photocatalytic coating.

20. The plastic substrate of claim 2, wherein a scratch-resistant or abrasion-resistant coating is inserted between the substrate and the coating intended to reduce the light reflectance.

21. A method for producing a substrate of claim 1, comprising the following steps:

forming a sol comprising at least one precursor of the material constituting the mesoporous structure of the coating and at least one organic structuring agent diluted in a solvent,

forming a mature sol,

adding a titanium dioxide nanoparticles or crystallites to the sol,

applying the sol to at least one surface of the substrate to be coated,

removing the solvent,

removing the organic structuring agent.

22. The method of claim 21, wherein, the substrate is made of plastic, the step of removing the solvent and the organic structuring agent is carried out at a temperature lower than or equal to 80°

C. under UV irradiation.

23. A glazing wherein it comprises a substrate as claimed in claim 1.

24. An ophthalmic lens which comprises the substrate of claim 19.

25. A method of using the substrate as claimed in claim 1, as a glazing for ophthalmic lenses, windows, aquarium glass, furniture, display screens, solar panels, automobiles, ships or aircraft, mirrors, automobile rearview mirrors, headlight optics, or lighting devices.