Three dimensional driving scheme for electrophoretic display devices
View Patent ↗The present invention is directed to a driving method, in particular a three dimensional driving scheme for electrophoretic display devices. The method comprises applying a driving step in each of at least two electric fields to drive two types of pigment particles of different colors laterally and/or vertically for separately adjusting the grayscale and/or colors of the display. The present driving method has the advantage that the brightness and color intensity of the images may be separately tuned.
1. A driving method for an electrophoretic display, wherein said display comprises a display cell layer comprising display cells and each of said display cells is filled with an electrophoretic fluid which fluid comprises at least two types of pigment particles of different colors dispersed in a solvent or solvent mixture, which method comprises simultaneously applying:
i) a voltage potential difference of ΔVx in an electric field between pixel electrodes in the X direction;
ii) a voltage potential difference of ΔVy in an electric field between pixel electrodes in the Y direction; and
iii) a voltage potential difference of ΔVz in an electric field between a common electrode and pixel electrodes in the Z direction.
2. The method of claim 1 , further comprising applying one or more of refreshing, dithering or pre-charging steps in any one or more of the electric fields.
3. The method of claim 1 , wherein the value ΔVx integrated over a time period (Δtx) is less than 1 Vsec.
4. The method of claim 1 , wherein the value ΔVy integrated over a time period (Δty) is less than 1 Vsec.
5. The method of claim 1 , wherein the value ΔVz integrated over a time period (Δtz) is less than 1 Vsec.
6. The method of claim 1 , wherein the sum of the value ΔV x integrated over a time period (Δt x ) and the value ΔV y integrated over a time period (Δt y ) is less than 2 Vsec.
7. The method of claim 1 , wherein the sum of the value ΔV y integrated over a time period (Δt y ) and the value ΔV z integrated over a time period (Δt z ) is less than 2 Vsec.
8. The method of claim 1 , wherein the sum of the value ΔV x integrated over a time period (Δt x ) and the value ΔV z integrated over a time period (Δt z ) is less than 2 Vsec.
9. The method of claim 1 , wherein the sum of the value ΔV x integrated over a time period (Δt x ), the value ΔV y integrated over a time period (Δt y ) and the value ΔV z integrated over a time period (Δt z ) is less than 3 Vsec.
10. The method of claim 1 , wherein the electric fields in the X and Y directions move the pigment particles laterally and the electric field in the Z direction moves the pigment particles vertically.
11. The method of claim 1 , wherein there are two types of pigment particles which are of the black and white colors respectively, dispersed in a clear solvent or solvent mixture.
12. The method of claim 11 , wherein the solvent or solvent mixture is colorless.
13. The method of claim 11 , wherein the solvent or solvent mixture is colored.
14. The method of claim 11 , wherein the solvent or solvent mixture is red, green, blue, cyan, magenta, yellow or a mixture thereof.
15. The method of claim 1 , wherein there are two type of pigment particles in which one type of pigment particles is white and the other type of pigment particles is red, green, blue, cyan, magenta, yellow or a mixture thereof.
16. The method of claim 15 , wherein the two types of pigment particles are dispersed in a black solvent or solvent mixture.
17. The method of claim 1 , wherein the solvent or solvent mixture and the pigment particles are of different colors.
18. The method of claim 1 , wherein the pigment particles have the same charge polarity or different charge polarities.
19. The method of claim 1 , wherein the pigment particles have the same threshold or different thresholds.
20. The method of claim 1 , wherein the pigment particles have the same degree of mobility or different degrees of mobility.
21. The method of claim 1 , wherein said electrophoretic fluid further comprising a charge controlling agent, polymeric additives, liquid crystal additives, nano-particles, nano-wires or nano-tubes.
22. The method of claim 1 , wherein shape of the pixel electrodes is rectangular, zig-zag, hexagonal, square, circular or triangular.
23. The method of claim 1 , wherein the pixel electrodes have the same size or different sizes.