Electrowetting system and method for operating
The present invention relates to an electrowetting system comprising an electrowetting element, a driver stage for applying a voltage to the element, and a switch connecting the electrowetting element to an output of the driver stage. The element comprises a first fluid and a second, immiscible fluid. The instantaneous position of the fluids is dependent on the voltage applied to the element, the voltage being set when the switch is closed. The voltage on the element is substantially maintained during a holding state longer than 70 ms when the switch is open.
1. An electrowetting system comprising an electrowetting element, a driver stage for applying a voltage to the electrowetting element, and a switch connecting the electrowetting element to an output of the driver stage, the electrowetting element comprising a first fluid and a second, immiscible fluid, an instantaneous position of the first and second fluids being dependent on the voltage applied to the electrowetting element, the voltage being set when the switch is closed, and the voltage on the electrowetting element being substantially maintained during a holding time longer than 70 ms when the switch is open, the holding time ending before or when a display state of the electrowetting element has reduced to 90% of a display state on opening the switch.
2. An electrowetting system according to claim 1 , wherein the holding time is longer than 250 ms.
3. An electrowetting system according to claim 1 , wherein the holding time is shorter than or equal to a backflow relaxation time of the electrowetting element.
4. An electrowetting system according to claim 1 , an extent of the first fluid being constrained to the electrowetting element.
5. An electrowetting system according to claim 1 , wherein the driver stage is arranged to apply a dc voltage to the electrowetting element.
6. An electrowetting system according to claim 1 , wherein the instantaneous position of the first and second fluids is substantially maintained during the holding time.
7. An electrowetting system according to claim 1 , comprising a capacitor connected to the electrowetting element.
8. An electrowetting system according to claim 1 , wherein the driver stage and the switch are integrated in a single element.
9. A display apparatus comprising a display controller, a plurality of driver stages, a plurality of electrowetting elements each comprising a first fluid and a second, immiscible fluid, an extent of the first fluid being constrained to the respective electrowetting element, and a plurality of switches connecting each electrowetting element to an output of a driver stage of the plurality of driver stages, the display controller having an input for receiving display data and an output for controlling the plurality of driver stages, each electrowetting element responding to an applied voltage as in claim 1 , and each electrowetting element showing a display state in response to the display data, a plurality of the display states forming a display.
10. A display apparatus according to claim 9 , comprising a capacitor connected to each electrowetting element.
11. A display apparatus according to claim 9 , wherein the display state includes grey levels.
12. A method for operating an electrowetting system comprising an electrowetting element, a driver stage for applying a voltage to the electrowetting element, and a switch connecting the electrowetting element to an output of the driver stage, the electrowetting element comprising a first fluid and a second, immiscible fluid, an extent of the first fluid being constrained to the electrowetting element, an instantaneous position of the first and second fluids being dependent on the voltage applied to the electrowetting element, including:
closing the switch and thereby setting the voltage; and
opening the switch during a holding state longer than 70 ms, while the voltage on the electrowetting element is substantially maintained, the holding state ending before or when a display state of the electrowetting element has reduced to 90% of a display state on opening the switch.
13. A method according to claim 12 , in which said closing and opening the switch are repeated.
14. A method according to claim 13 , wherein a duration of the holding state depends on when a display state change of the electrowetting element is needed.
15. A method according to claim 13 , wherein a duration of the holding state depends on a required frame rate.