Electrowetting device

1. An electrowetting display device comprising a picture element comprising a first fluid and a second fluid immiscible with the first fluid, the picture element having a display area and at least one wall forming a perimeter of the display area and confining the first fluid to the display area, wherein the at least one wall comprises a first surface and a second surface at different locations on the perimeter, the first surface being less wettable to the second fluid than the second surface.

2. An electrowetting display device according to claim 1 , a configuration of the first and second fluids being switchable in dependence on a voltage applied to the second fluid, wherein when switching from a first configuration with a zero applied voltage, to a different, second configuration with a non-zero applied voltage, a motion of the first fluid initiates at the first surface before initiating at the second surface.

3. An electrowetting display device according to claim 2 , wherein the first surface and the second surface are arranged relative to each other to provide a preferential direction of motion of the first fluid when switching from the first configuration to the second configuration.

4. An electrowetting display device according to claim 2 , the at least one wall comprising a third surface and a fourth surface, the third surface having substantially the same wettability to the second fluid as the first surface and the fourth surface having substantially the same wettability to the second fluid as one or more of: the first surface and the second surface, wherein the first, second, third and fourth surfaces are arranged relative to each other to provide a preferential direction of motion of the first fluid when switching from the first configuration to the second configuration.

5. An electrowetting display device according to claim 1 , wherein the at least one wall comprises a third surface and a fourth surface each having substantially the same wettability to the second fluid as the first surface.

6. An electrowetting display device according to claim 1 , wherein the at least one wall comprises a third surface having substantially the same wettability to the second fluid as the first surface, and a fourth surface having substantially the same wettability to the second fluid as the second surface.

7. An electrowetting display device according to claim 1 , the at least one wall comprising a third surface and a fourth surface, the third surface having substantially the same wettability to the second fluid as the first surface and the fourth surface having substantially the same wettability to the second fluid as one or more of: the first surface and the second surface, wherein the first, second, third and fourth surfaces form one or more of: a square or rectangular display area perimeter.

8. An electrowetting display device according to claim 1 , wherein when a zero voltage is applied to the second fluid, the first fluid wets the first surface with a first contact angle and the first fluid wets the second surface with a second contact angle, the first contact angle being less than the second contact angle.

9. An electrowetting display device according to claim 8 , wherein the first contact angle is less than 90 degrees.

10. An electrowetting display device according to claim 8 , wherein the second contact angle is greater than one or more of: 90 degrees, 95 degrees and 100 degrees.

11. An electrowetting display device according to claim 8 , wherein when the zero voltage is applied to the second fluid, the second fluid wets the first surface with a third contact angle and the second fluid wets the second surface with a fourth contact angle, the third contact angle being greater than the fourth contact angle.

12. An electrowetting display device according to claim 11 , wherein the first contact angle is less than 90 degrees and the third contact angle is greater than 90 degrees.

13. An electrowetting display device according to claim 11 , wherein the second contact angle is greater than one or more of: 90 degrees, 95 degrees and 100 degrees and the fourth contact angle is less than one or more of: 90 degrees, 85 degrees and 80 degrees.

14. An electrowetting display device according to claim 1 , wherein the first surface is hydrophobic and the second surface is hydrophilic.

15. An electrowetting display device according to claim 1 , wherein a surface of the display area joins the first surface and has substantially the same wettability to the second fluid as the first surface.

16. An electrowetting display device according to claim 15 , wherein the first surface and the surface of the display area are formed from a continuous layer of material less wettable to the second fluid than the second surface.

17. An electrowetting display device according to claim 16 , the at least one wall comprising a third surface and a fourth surface, the third surface having substantially the same wettability to the second fluid as the first surface and the fourth surface having substantially the same wettability to the second fluid as the first surface, wherein said continuous layer comprises the third surface and the fourth surface.

18. An electrowetting display device according to claim 16 , the at least one wall comprising a third surface and a fourth surface, the third surface having substantially the same wettability to the second fluid as the first surface and the fourth surface having substantially the same wettability to the second fluid as the second surface, wherein said continuous layer comprises the third surface.

19. A support plate for an electrowetting display device comprising a picture element comprising a first fluid and a second fluid immiscible with the first fluid, the support plate comprising a display area for the picture element and at least one wall forming a perimeter of the display area and suitable for confining the first fluid to the display area, wherein the at least one wall comprises a first surface and a second surface at different locations of the perimeter, the first surface being less wettable for the second fluid than the second surface.

20. An electrowetting device comprising a first fluid, a second fluid immiscible with the first fluid, and at least one wall confining the first fluid, wherein the at least one wall comprises a first surface which, when a zero voltage is applied to the second fluid, is wet by the first fluid with a first contact angle of less than 90 degrees.

21. An electrowetting device according to claim 20 , wherein one or more of the following apply: the first surface extends over a height of the at least one wall, the first surface is a face of the at least one wall, and the first surface is hydrophobic.

22. An electrowetting device according to claim 20 , wherein the first contact angle is less than one or more of: 85 degrees and 80 degrees.

23. An electrowetting device according to claim 20 , wherein when a zero voltage is applied to the second fluid, the second fluid wets the first surface with a third contact angle of greater than 90 degrees.

24. An electrowetting device according to claim 20 , wherein the electrowetting device is an electrowetting display device comprising a picture element which comprises the first and second fluids, the at least one wall forming a perimeter of a display area of the picture element.

25. A support plate for an electrowetting display device comprising a picture element comprising a first fluid and a second fluid immiscible with the first fluid, the support plate comprising a display area for the picture element and at least one wall providing a perimeter of the display area and suitable for confining the first fluid to the display area, wherein the at least one wall comprises a first surface which, when a zero voltage is applied to the second fluid, is wet by the first fluid with a first contact angle of less than 90 degrees.