Driving of electrowetting display device

1. A method of driving an electrowetting display device including a display element, the display element having an electrode for applying a voltage and providing a display state in response to a signal level of the voltage, the method comprising the following subsequent steps for maintaining a display state of the display element:

applying a first signal level during a first period for providing the display state;

applying a second signal level different from the first signal level during a second period while substantially maintaining a perceived display state of the first period; and

applying the first signal level during a third period;

the first period being longer than 1 ms and the sum of the first period and the third period being longer than five times the second period.

2. A method of driving an electrowetting display device including a display element, the display element having an electrode for applying a voltage and providing a display state in response to a signal level of the voltage, the method comprising the following subsequent steps for maintaining a display state of the display element:

applying a first signal level during a first period for providing the display state;

applying a second signal level different from the first signal level during a second period while substantially maintaining a perceived display state of the first period; and

applying the first signal level during a third period;

a display state during the second period being different from a display state prior to application of the second signal level.

3. A method according to claim 1 or 2 , wherein the first period is shorter than three times a relaxation time t rel of the display element.

4. A method according to claim 3 , wherein the first period having a duration of t 1 and the second period having a duration of t 2 comply with

1/ t 1 >αt 2 /t r +β for t 2 /t r >−β/α and

1/ t 1 >0 for t 2 /t r ≦−β/α,

t r being a response time of the element and α and β being constants equal to 62 s −1 and −38 s −1 when t 1 <t rel and equal to 68 s −1 and −38 s −1 when t 1 ˜t rel .

5. A method according to claim 3 , wherein the first period having a duration of t 1 and the second period having a duration of t 2 comply with

1/ t 1 >αt 2 /t r +β for t 2 /t r >−1.4 β/α and

1/ t 1 >0 for t 2 /t r ≦−1.4β/α,

t r being a response time of the element and α and β being constants equal to 90 s −1 and −40 s −1 when t 1 <t rel and equal to 100 s −1 and −40 s −1 when t 1 ˜t rel .

6. A method according to claim 3 , wherein the first period is longer than 10 ms.

7. A method according to claim 1 or 2 , including carrying out the last two of said subsequent steps at the end of the third period.

8. A method according to claim 1 or 2 , wherein the display element attains a first extreme display state at a low signal level and a second extreme display state at a high signal level, the magnitude of the second voltage being less than ⅕ of the high signal level.

9. A method according to claim 1 or 2 , wherein the first period and the third period are longer than 10 times the duration of the second period.

10. A display driving system for an electrowetting display device having a display element including an electrode, the display driving system including a data input for receiving data signals, each data signal selecting a display element and providing a display state for the display element, an output of the display driving system being connected to the electrode for applying a voltage having the signal level pertaining to the display state, the display driving system being arranged to perform the method of claims 1 or 2 .

11. A display driving system according to claim 10 , including a signal distributor having an input connected to the data input and a plurality of distributor outputs; and

a driver assembly including one or more driver stages, each driver stage having an input connected to one of the distributor outputs.

12. A display driving system according to claim 11 , wherein each driver stage has a driver stage output connected to at least one electrode of the display element.

13. A display driving system according to claim 11 , wherein the display device includes a plurality of elements arranged in columns and/or rows and each driver stage has a driver stage output connected to a column electrode or a row electrode.

14. A display driving system according to claim 10 , including a generator for forming pulses having a voltage of the second signal level and a duration of the second interval and having an output connected to the data input or to a driver assembly.

15. A display driving system according to claim 10 adapted for driving a transmissive, reflective or transflective display device.

16. An electro-optic display apparatus including a display driving system according to claim 10 and a display device.