Driving methods for electrophoretic displays
View Patent ↗The present invention is directed to driving methods for driving a color display device which can display high quality color states. The display device utilizes an electrophoretic fluid which comprises three types of pigment particles having different optical characteristics.
1. A driving method for driving an electrophoretic display comprising a first surface on a viewing side, a second surface on a non-viewing side, and an electrophoretic fluid sandwiched between a common electrode and a layer of pixel electrodes; the electrophoretic fluid comprises a first type of pigment particles, a second type of pigment particles, and a third type of pigment particles, all of which are dispersed in a solvent or solvent mixture, wherein
(a) the three types of pigment particles have optical characteristics differing from one another;
(b) the first type of pigment particles and the second type of pigment particles carry opposite charge polarities; and
(c) the third type of pigment particles has the same charge polarity as the second type of pigment particles but at a lower intensity;
the method comprises the following steps:
(i) driving a pixel in the electrophoretic display to the color state of the first type of pigment particles or the color state of the second type of pigment particles;
(ii) applying a first driving voltage to the pixel in the color state of the first type of pigment particles for a first period of time, wherein the first driving voltage has the same polarity as the second type of pigment particles and the duration of the first period of time is configured to drive the pixel to a grey state between the color state of the first type of pigment particle and the color state of the second type of pigment particles, or applying a second driving voltage to the pixel in the color state of the second type of pigment particles for a second period of time, wherein the second driving voltage has the same polarity as the first type of pigment particles and the duration of the second period of time is configured to drive the pixel to a grey state between the color state of the second type of pigment particle and the color state of the first type of pigment particles; and
(iii) applying a shaking waveform, wherein the shaking waveform is applied immediately after either one of the first period of time or the second period of time.
2. The method of claim 1 , wherein the first type of pigment particles is negatively charged and the second type of pigment particles is positively charged.
3. The method of claim 1 , wherein the three types of pigment particles have different colors.
4. The method of claim 1 , wherein the first type of pigment particles is white and the second type of pigment particles is black.
5. The method of claim 1 , wherein the third type of pigment particles is non-white and non-black.
6. The method of claim 1 , wherein the third type of pigment particles is red.
7. The method of claim 1 , further comprising applying a driving voltage having the same polarity as the first type of pigment particles to drive the pixel to the color state of the first type of pigment particles at the viewing side.
8. The method of claim 1 , further comprising applying a driving voltage having the same polarity as the second type of pigment particles to drive the pixel to the color state of the second type of pigment particles at the viewing side.
9. The method of claim 1 , further comprising applying a driving voltage having the same polarity as the third type of pigment particles to drive the pixel to the color state of the third type of pigment particles at the viewing side.