Electrowetting element, display device and control system

1. An electrowetting element for a display device, wherein the electrowetting element comprises:

a) a radiation valve comprising a first fluid and a second fluid immiscible with the first fluid, wherein the first and second fluids are configurable to change a characteristic of radiation passing through at least one of said first and second fluids; and

b) an electrically switchable part switchable between a reflective mode for reflecting radiation incident on the switchable part and towards said radiation valve, and a transmissive mode for transmitting radiation incident on the switchable part through said switchable part and towards said radiation valve,

wherein said switchable part includes a reflective fluid and a non-reflective fluid immiscible with the reflective fluid, the reflective and non-reflective fluids being configurable to switch said reflective and non-reflective fluids between the transmissive mode and the reflective mode.

2. An electrowetting element according to claim 1 , including a support plate arranged between said switchable part and said radiation valve to support mechanically the switchable part and the radiation valve.

3. An electrowetting element according to claim 1 , wherein the electrowetting element is arranged for a control system to apply a first voltage across at least one of said first and second fluids and to apply a second voltage to said switchable part.

4. An electrowetting element according to claim 1 , wherein said switchable part is integrated with said radiation valve, said second fluid being said non-reflective fluid, wherein only said second fluid separates said first fluid and said reflective fluid.

5. An electrowetting element according to claim 1 , wherein said switchable part includes a layer of polymer dispersed liquid crystal (PDLC) and is switchable between the transmissive and reflective modes by application of a voltage across said PDLC layer.

6. An electrowetting element according to claim 1 , wherein said radiation valve includes at least one further fluid which is immiscible with at least one of said first and second fluids or with a second further fluid, said at least one further fluid being configurable between different fluid configurations to change said characteristic of the radiation.

7. An electrowetting element according to claim 1 , wherein said electrowetting element comprises a first colour filter arranged to filter radiation passing through at least part of the electrowetting element.

8. An electrowetting element according to claim 7 , wherein at least one of said first, second and at least one further fluid includes said first colour filter.

9. An electrowetting element according to claim 7 , wherein said electrowetting element comprises a second colour filter, said first and second colour filters being arranged such that, with the switchable part being in the reflective mode, radiation passing through the electrowetting element passes at least twice through said first colour filter only, and, with the switchable part being in the transmissive mode, radiation passing through the electrowetting element passes at least once through each of said first and second colour filters.

10. An electrowetting element according to claim 1 , wherein one of said fluids is arranged to absorb substantially all radiation passing through at least part of said electrowetting element.

11. An electrowetting element according to claim 1 , wherein said switchable part is switchable to provide an intermediate mode for reflecting radiation incident on the switchable part towards said radiation valve and for transmitting radiation incident on the switchable part through said switchable part and towards said radiation valve.

12. An electrowetting element according to claim 1 , wherein said electrowetting element comprises a radiation emitter arranged to emit radiation for transmission through said switchable part.

13. A display device comprising a plurality of the electrowetting element according to claim 1 , and a control system arranged to control electrically each of said plurality of electrowetting elements.

14. A display device according to claim 13 , wherein said control system is arranged to switch simultaneously the switchable part of each of said plurality of electrowetting elements between the reflective mode and the transmissive mode and/or to switch the fluids between different configurations.

15. A display device according to claim 14 , wherein said control system is arranged to switch the switchable part of one of the plurality of electrowetting elements between the reflective mode and the transmissive mode, and/or to configure the first and second fluids, separately from a different one of the plurality of electrowetting elements.

16. A display device according to claim 13 , wherein said control system is arranged to apply a first voltage across at least one of said first and second fluids of the radiation valve of at least one electrowetting element and to apply a second voltage to said switchable part of at least one electrowetting element.

17. A display device according to claim 16 , wherein the control system is arranged to apply said first and second voltages in accordance with a maximum voltage set to provide said switching of the switchable part independently of said configuring of the first and second fluids.

18. A display device according to claim 16 , wherein the control system is arranged to apply said first and second voltages in accordance with a voltage timing pattern determined to provide said switching of the switchable part independently of said configuring of the first and second fluids.

19. A display device according to claim 16 , wherein said switchable part is electrically isolated from said radiation valve, and said control system is arranged to apply said first and second voltages in accordance with an extent of said electrical isolation.

20. A display device according to claim 13 , wherein said display device includes an ambient radiation detector and the control system is arranged to switch the switchable part in accordance with an output signal of the ambient radiation detector.

21. A control system arranged to control at least one electrowetting element in accordance with claim 1 , wherein said control system is arranged to apply a first voltage across at least one of said first and second fluids of the radiation valve of the at least one electrowetting element and to apply a second voltage to said switchable part of the at least one electrowetting element.

22. A control system according to claim 21 , wherein the control system is arranged to apply said first and second voltages in accordance with a maximum voltage set to provide said switching of the switchable part independently of said configuring of the first and second fluids.

23. A control system according to claim 21 , wherein the control system is arranged to apply said first and second voltages in accordance with a voltage timing pattern determined to provide said switching of the switchable part independently of said configuring of the first and second fluids.

24. A control system according to claim 21 , wherein said switchable part is electrically isolated from said radiation valve, and said control system is arranged to apply said first and second voltages in accordance with an extent of said electrical isolation.