Coated glass
Dual coated glass sheets comprise a photocatalytically active self cleaning coating on one surface and heat reflecting coating on the second surface selected so that its single surface reflectivity is either at least three times or less than one third that of the self cleaning coating. The selection of the heat reflecting coating provides a sheet having an improved appearance. Such dual coated sheets combine self cleaning properties with solar control or low emissivity properties and are useful as building glasses.
1. A dual coated self cleaning glazing sheet which comprises on a first surface thereof a photocatalytically active hydrophilic coating with a single surface reflectivity of less than 20% and on the second surface thereof a functional coating having a single surface reflectivity of of less than 5% or greater than 30%, wherein the composition and properties of each of said coatings is chosen such that said functional coating has a single surface reflectivity of less than one third or more than three times that of the photocatalytically active hydrophilic coating.
2. A dual coated glazing sheet according to claim 1 , wherein the functional coating is a heat reflecting coating.
3. A glazing sheet according to claim 1 , wherein the photocatalytically active hydrophilic coating has a single surface reflectivity of less than 15%.
4. A glazing sheet according to claim 3 , wherein the photocatalytically active hydrophilic coating has a single surface reflectivity of less than 10%.
5. A glazing sheet according to claim 1 , wherein the photocatalytically active hydrophilic coating comprises titanium dioxide.
6. A glazing sheet according to claim 5 , wherein the titanium dioxide coating is from 10 to 20 nm thick.
7. The glazing sheet according to claim 1 , wherein the photocatalytically active hydrophilic coating comprises an underlayer which is an alkali metal ion blocking layer.
8. The glazing sheet according to claim 7 , wherein the underlayer comprises a silicon oxide.
9. The glazing sheet according to either of claim 7 , wherein the underlayer is from 25 to 40 nm thick.
10. The glazing sheet according to claim 1 , wherein the functional coating has a single surface reflectivity of less than 5%.
11. The glazing sheet according to claim 10 , wherein the functional coating has a single surface reflectivity of less than 3%.
12. The glazing sheet according to claim 1 , wherein the single surface reflectivity of the functional coating is greater than 30%.
13. A glass laminate comprising at least two glass panes separated by a bonding interlayer disposed between them wherein one of the glass panes comprises a dual coated sheet according to claim 1 .
14. A multiple glazing unit comprising at least two glass panes spaced apart by a perimeter seal wherein at least one of the glass panes comprises a dual coated glass according to claim 1 .
15. A glass laminate comprising at least two glass panes separated by a bonding interlayer wherein a first of said at least two panes has a photocatalytically active hydrophilic coating on an exterior surface thereof with a single surface reflectivity of less than 20% and a second of said at least two glass panes has a functional coating upon at least one surface thereof having a single surface reflectivity of of less than 5% or greater than 30%, wherein the composition and properties of each of said coatings is chosen such that the functional coating has a single surface reflectivity which is less than one third or more than three times that of the photocatalytically active coating of the first pane.
16. A multiple glazing unit comprising at least two glass panes spaced apart by a perimeter seal wherein a first of the panes has a photocatalytically active hydrophilic coating on an exterior surface thereof with a single surface reflectivity of less than 20% and a second of the at least two glass panes has a functional coating upon at least one surface having a single surface reflectivity of of less than 5% or greater than 30%, wherein the composition and properties of each of said coatings is chosen such that the functional coating has a single surface reflectivity which is less than one third or more than three times that of the photocatalytic coating of the first glass pane.