Color display device

• US 9,759,981 B2
• Filed: 01/30/2017
• Issued: 09/12/2017
• Est. Priority Date: 03/18/2014
• Status: Active Grant

• Current Assignee: E Ink Corporation (E Ink Holdings Incorporated)
• Original Assignee: E Ink California, LLC (E Ink Holdings Incorporated)
• Inventors: Wang, Ming, Laxton, Peter B., Li, Yu
• Primary Examiner(s): Martinez, Joseph P
• Application Number:
  US15/419,391
• Publication Number:
  US 20170139304A1
• Time in Patent Office: 225 Days
• CPC Class Codes: G02F 1/167 by electrophoresis
• CPC Class Codes: G02F 1/1685 Operation of cells; Circuit arrangements affecting the entire cell
• CPC Class Codes: G02F 2001/1678 characterised by the composition or particle type
• CPC Class Codes: G02F 2202/32 Photonic crystals
• CPC Class Codes: G02F 2203/34 Colour display without the use of colour mosaic filters

Abstract

The present invention provides a reflective color display device which can display multiple color states, without the disadvantages associated with previously known color display devices. The display fluid of the present invention comprises (a) black and white electrophoretic particles which are oppositely charged and (b) charged color-generating particles having photonic crystal characteristics, all of which are dispersed in a solvent or solvent mixture.

Claims

1. A method for displaying colors, the method comprising:

providing a layer of a display fluid, the layer having a viewing surface, the display fluid comprising first electrophoretic particles bearing a charge of one polarity, second electrophoretic particles bearing a charge of the opposite polarity, one or the first and second particles being white and the other black, and charged third particles bearing a charge of the same polarity as the first particles, the third particles having photonic crystal characteristics in as much as the wavelength of light reflected from a grouping of the third particles varies with the distance between the particles, the first, second and third particles all being dispersed in a solvent or solvent mixture, the method comprising;

(i) applying a first electric field having a high magnitude and a polarity driving the first particles towards the viewing surface, thereby causing the color of the first particles to be displayed at the viewing surface;

(ii) applying a second electric field having a high magnitude and a polarity driving the second particles towards the viewing surface, thereby causing the color of the second particles to be displayed at the viewing surface;

(iii) when the color of the second particles is displayed at the viewing surface, applying a third electric field having the same polarity as, but a lower magnitude than, the first electric field, thereby causing the color of the dispersed third particles to be displayed at the viewing surface; and

(iv)when the color of the dispersed third particles is displayed at the viewing surface, applying a fourth electric field having the same polarity as the first and third electric fields, and a magnitude intermediate the magnitudes of the first and third electric fields, thereby causing to be displayed at the viewing surface a fourth color which is different from all of black, white and the color of the dispersed third particles.

2. The method of claim 1 wherein, when the color of the first particles is displayed at the viewing surface, applying a fifth electric field having the same polarity as, but a lower magnitude than, the second electric field, thereby causing the color of the dispersed third particles to be displayed at the viewing surface.

3. The method of claim 1 wherein, when the fourth color is displayed at the viewing surface, applying a color-changing electric field having the same polarity as the first and fourth electric fields, and a magnitude intermediate the magnitude of the first and fourth electric fields, thereby causing to be displayed at the viewing surface a fifth color which is different from all of black, white, the color of the dispersed third particles, and the fourth color.

4. The method of claim 3 wherein the color of the dispersed third particles, the fourth color and the fifth color are red, green and blue respectively.

5. The method of claim 1 wherein the intensity of the colors displayed is controlled by adjusting locations of the black and white electrophoretic particles or mixing levels of the black and white particles.

6. A display device comprising a layer of a display fluid, the layer having a viewing surface, the display fluid comprising first electrophoretic particles bearing a charge of one polarity, second electrophoretic particles bearing a charge of the opposite polarity, one or the first and second particles being white and the other black, and charged third particles bearing a charge of the same polarity as the first particles, the third particles having photonic crystal characteristics in as much as the wavelength of light reflected from a grouping of the third particles varies with the distance between the particles, the first, second and third particles all being dispersed in a solvent or solvent mixture, and means for applying an electric field across the layer of the display fluid, the display device being characterized in that:

(i) applying a first electric field having a high magnitude and a polarity driving the first particles towards the viewing surface causes the color of the first particles to be displayed at the viewing surface;

(ii) applying a second electric field having a high magnitude and a polarity driving the second particles towards the viewing surface causes the color of the second particles to be displayed at the viewing surface;

(iii)when the color of the second particles is displayed at the viewing surface, applying a third electric field having the same polarity as, but a lower magnitude than, the first electric field causes the color of the dispersed third particles to be displayed at the viewing surface;

(iv)when the color of the dispersed third particles is displayed at the viewing surface, applying a fourth electric field having the same polarity as the first and third electric fields, and a magnitude intermediate the magnitudes of the first and third electric fields, causes to be displayed at the viewing surface a fourth color which is different from all of black, white and the color of the dispersed third particles.

7. The display device of claim 6 wherein the third particles have electrical polarization characteristics.

8. The display device of claim 6 wherein the solvent or solvent mixture has electrical polarization characteristics.

9. The display device of claim 6 wherein both the third particles and the solvent or solvent mixture have electrical polarization characteristics.

10. The display device of claim 6 wherein the third particles are formed of silicon (Si), titanium (Ti), barium (Ba), strontium (Sr), iron (Fe), nickel (Ni), cobalt (Co), lead (Pb), aluminum (Al), copper (Cu), silver (Ag), gold (Au), tungsten (W), molybdenum (Mo), or a compound thereof.

11. The display device of claim 6 wherein the third particles are formed of polymer materials such as PS (polystyrene), PE (polyethylene), PP (polypropylene), PVC (polyvinyl chloride), or PET (polyethylene terephthalate).

12. The display device of claim 6 wherein the third particles are formed by coating particles or a cluster having no electric charge with a material having electric charges.

13. The display device of claim 7 wherein the third particles include a material which is electrically polarized with any one of electronic polarization, ionic polarization, interfacial polarization or rotational polarization due to asymmetrical charge distribution of atoms or molecules as an external electric field is applied.

14. The display device of claim 6 wherein the third particles include a ferroelectric material.

15. The display device of claim 6 wherein the third particles include a superparaelectric material.

16. The display device of claim 6 wherein the third particles include a material having a perovskite structure.

17. The display device of claim 6 wherein the solvent is water, trichloroethylene, carbon tetrachloride, di-iso-propyl ether, toluene, methyl-t-butyl ether, xylene, benzene, diethyl ether, dichloromethane, 1,2-dichloroethane, butyl acetate, iso-propanol, n-butanol, tetrahydrofuran, n-propanol, chloroform, ethyl acetate, 2-butanone, dioxane, acetone, methanol, ethanol, acetonitrile, acetic acid, dimethylformamide, dimethyl sulfoxide or propylene carbonate.