Driving methods for color display devices
The present invention provides driving methods for electrophoretic color display devices. The backplane system used for the driving methods is found to be simpler which renders color display devices more cost effective. More specifically, the driving method comprises first driving all pixels towards a color state by modulating only the common electrode, followed by driving all pixels towards their desired color states by maintaining the common electrode grounded and applying different voltages to the pixel electrodes.
1. A driving method for a display device, wherein the display device comprises:
(i) an electrophoretic fluid comprising a first type of particles, a second type of particles, and a third type of particles, all of which are dispersed in a solvent or solvent mixture, wherein the first type of particles carry a charge polarity while the second and third types of particles carry an opposite charge polarity, and
(ii) a plurality of pixels wherein each pixel is sandwiched between a common electrode and a pixel electrode; the method comprises the steps of:
a) applying no voltage to the pixel electrodes and applying a high voltage to the common electrode, wherein the high voltage has a polarity opposite to the charge polarity of the first type of particles, to drive all pixels towards the color state of the first type of particles;
b) applying no voltage to the pixel electrodes and applying a low voltage to the common electrode, wherein the low voltage has a polarity opposite to the charge polarity of the third type of particles, to drive all pixels towards the color state of the third type of particles; and
c) maintaining the common electrode grounded and applying different voltages to the pixel electrodes to drive pixels towards their desired color states.
2. The driving method of claim 1 , in step (c), no voltage is applied to the pixel electrodes to maintain the pixels in the color state of the third type of particles.
3. The driving method of claim 1 , in step (c), a high voltage is applied to the pixel electrodes wherein the high voltage has the same polarity as the second type of particles to drive the pixels towards the color state of the second type of particles.
4. The driving method of claim 1 , in step (c), a high voltage is applied to the pixel electrodes wherein the high voltage has the same polarity as the first type of particles to drive the pixels towards the color state of the first type of particles.
5. The driving method of claim 1 , further comprising a shaking waveform prior to step (a).
6. The driving method of claim 1 , wherein the first type of particles is negatively charged and the second and third types of particles are positively charged.
7. The driving method of claim 1 , wherein the first type of particles is white particles, the second type of particles is black particles and the third type of particles is non-white and non-black particles.