Color display device
The present invention provides a solution for a highlight or multicolor display device, in which each display cell can display high quality color states. More specifically, an electrophoretic fluid is provided which comprises three types of pigment particles, having different levels of size, threshold voltage or charge intensity.
1. A display layer having a first viewing surface and a second surface on the opposed side of the display layer from the first surface, the display layer comprising a common electrode adjacent the first surface and a plurality of pixel electrodes adjacent the second surface, the pixel electrodes defining pixels of the display layer, the display layer further comprising an electrophoretic fluid disposed between the common electrode and the pixel electrodes, the electrophoretic fluid comprising a solvent or solvent mixture and first, second and third types of particles dispersed in the solvent or solvent mixture, the first, second and third types of particles having respectively first, second and third optical characteristics differing from one another, the first type of particles having a charge of one polarity and the second and third types of particles having charges of the opposite polarity, and the second type of particles having a threshold voltage, such that:
(a) application of a potential difference greater than the threshold voltage between the common electrode and a pixel electrode, which potential difference has a polarity which causes the second type of particles to move adjacent the first surface, causes the associated pixel to display the second optical characteristic at the first surface;
(b) application of a potential difference greater than the threshold voltage between the common electrode and a pixel electrode, which potential difference has a polarity which causes the first type of particle to move adjacent the first surface, causes the associated pixel to display the first optical characteristic at the first surface; or
(c) once the first optical characteristic is displayed at the first surface, application of a potential difference the same as, or lower than, the threshold voltage between the common electrode and a pixel electrode, which potential difference has a polarity which causes the third type of particles to move adjacent the first surface, causes the associated pixel to display the third optical characteristic at the first surface.
2. The layer of claim 1 , wherein the first and second optical characteristics are white and black, respectively.
3. The layer of claim 1 , wherein the third optical characteristic is non-white and non-black.
4. The layer of claim 3 , wherein the third optical characteristic is selected from the group consisting of red, green, blue, magenta, yellow and cyan.
5. The layer of claim 1 , wherein the third type of particles is larger than the first and second types of particles.
6. The layer of claim 5 , wherein the third type of particles is about 2 to about 50 times the sizes of the first and second types of particles.
7. The layer of claim 1 , wherein the first, second and third optical characteristics are colors.
8. The layer of claim 1 , wherein the electrophoretic fluid is held within display cells.
9. The layer of claim 8 , wherein the display cells are aligned with the pixel electrodes.
10. The layer of claim 8 , wherein the display cells are not aligned with the pixel electrodes.
11. The layer of claim 8 wherein the third type of particles is of the same color in all display cells.
12. The layer of claim 8 , wherein the third type of particles is of different colors in different display cells.
13. The layer of claim 1 , wherein in (c), the potential difference is applied for not longer than 30 seconds.
14. The layer of claim 13 , wherein in (c), the potential difference is applied for not longer than 15 seconds.
15. A driving method for a display layer having a first viewing surface and a second surface on the opposed side of the display layer from the first surface, the display layer comprising a common electrode adjacent the first surface and a plurality of pixel electrodes adjacent the second surface, the pixel electrodes defining pixels of the display layer, the display layer further comprising an electrophoretic fluid disposed between the common electrode and the pixel electrodes, the electrophoretic fluid comprising a solvent or solvent mixture and first, second and third types of particles dispersed in the solvent or solvent mixture, the first, second and third types of particles having respectively first, second and third optical characteristics differing from one another, the first type of particles having a charge of one polarity and the second and third types of particles having charges of the opposite polarity, and the second type of particles having a threshold voltage, which method comprises:
(a) applying a potential difference greater than the threshold voltage between the common electrode and a pixel electrode, which potential difference has a polarity which causes the second type of particles to move adjacent the first surface, thereby causing the associated pixel to display the second optical characteristic at the first surface;
(b) applying a potential difference greater than the threshold voltage between the common electrode and a pixel electrode, which potential difference has a polarity which causes the first type of particle to move adjacent the first surface, thereby causing the associated pixel to display the first optical characteristic at the first surface; or
(c) once the first optical characteristic is displayed at the first surface, applying a potential difference between the common electrode and a pixel electrode, which potential difference is the same as, or lower than, the threshold voltage and has a polarity which causes the third type of particles to move adjacent the first surface, thereby causing the associated pixel to display the third optical characteristic at the first surface.
16. The method of claim 15 , wherein in step (c), the potential difference is applied for not longer than 30 seconds.
17. The method of claim 16 , wherein in step (c), the potential difference is applied for not longer than 15 seconds.
18. The driving method of claim 15 , further comprising applying a shaking waveform before step (a).
19. A driving method for a display layer having a first viewing surface and a second surface on the opposed side of the display layer from the first surface, the display layer comprising a common electrode adjacent the first surface and a plurality of pixel electrodes adjacent the second surface, the pixel electrodes defining pixels of the display layer, the display layer further comprising an electrophoretic fluid disposed between the common electrode and the pixel electrodes, the electrophoretic fluid comprising a solvent or solvent mixture and first, second and third types of particles dispersed in the solvent or solvent mixture, the first, second and third types of particles having respectively first, second and third optical characteristics differing from one another, the first type of particles having a charge of one polarity and the second and third types of particles having charges of the opposite polarity, and the second type of particles having a threshold voltage, which method comprises driving a pixel of the first surface from the first optical characteristic to the third optical characteristic by applying between the common electrode and a pixel electrode of the pixel a potential difference the same as, or less than, the threshold voltage of the second type of particles.