Transmissive electrophoretic display with laterally adjacent color cells

• US 6,184,856 B1
• Filed: 09/16/1998
• Issued: 02/06/2001
• Est. Priority Date: 09/16/1998
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Gordon, Joseph Grover II, Hart, Mark Whitney, Swanson, Sally Ann
• Primary Examiner(s): Saras, Steven J.
• Assistant Examiner(s): Bell, Paul A.
• Application Number:
  US09/154,626
• Time in Patent Office: 874 Days
• Field of Search: 345/48, 345/55, 345/84, 345/107, 359/296, 430/32-38
• US Class Current: 345/107
• CPC Class Codes: G02F 1/167 by electrophoresis
• CPC Class Codes: G02F 1/1677 Structural association of cells with optical devices, e.g. reflectors or illuminating devices

Abstract

A transmissive electrophoretic color display is comprised of a plurality of color pixels; each uniformly illuminated from the rear by a backlight and each comprised of at least two electrophoretic cells. Each cell is comprised of a suspension of charged, black or colored light-absorbing pigment particles in a light-transmissive fluid. Each cell is also comprised of a light-transmissive front and rear window, at least one non-obstructing counter electrode, at least one non-obstructing collecting electrode, and a color filter medium. The cells of different colors are in a laterally adjacent relationship to each other and the charged pigment particles are responsive to the electrodes. The filter medium in each cell can be a light-transmissive color filter element or the pigment suspension fluid can be colored and serve as the filter medium.

Claims

1. An electrophoretic display comprising:

a light-transmissive rear window;

a light-transmissive front window;

a plurality of cells located between the rear and front windows, each cell containing charged light-absorbing pigment particles in a light-transmissive fluid, and wherein laterally adjacent cells are grouped together to form multicolor pixels;

a collecting electrode positioned within each cell to be substantially nonobstructive to light for collecting pigment particles in the cells to remove them out of the path of light when the rear window is illuminated from behind so that light can reach the front window without significant attenuation;

a counter electrode substantially non-obstructive to light and cooperative with the collecting electrode for dispersing the pigment particles generally uniformly throughout the light-transmissive fluid in the cells, whereby the dispersed pigment particles substantially block the path of light when the rear window is illuminated from behind so that the light is significantly attenuated before reaching the front window; and

a color filter medium associated with each cell for displaying an associated color at the front window when the rear window is illuminated from behind and the pigment particles are located on the collecting electrode.

2. The display according to claim 1 wherein the color filter medium associated with each cell is a colored filter element, the color of each filter element in a cell of a pixel being different from the colors of the filter elements associated with the other cells of the same pixel.

3. The display according to claim 2 wherein each filter element is located between the respective cell and the front window.

4. The display according to claim 2 wherein each filter element is located within the front window.

5. The display according to claim 2 wherein each filter element is located on the front surface of the front window.

6. The display according to claim 2 wherein each filter element is located between the respective cell and the rear window.

7. The display according to claim 2 wherein each filter element is located within the rear window.

8. The display according to claim 2 wherein each filter element is located on the outer surface of the rear window.

9. The display according to claim 2 wherein there are three cells for each pixel, wherein a first cell includes a red filter element, a second cell includes a green filter element, and a third cell includes a blue filter element.

10. The display according to claim 9 wherein the pigment particles in all of the cells are black.

11. The display according to claim 9 wherein the pigment particles in the cell having the red filter element are cyan, the pigment particles in the cell having the green filter element are magenta, and the pigment particles in the cell having the blue filter element are yellow.

12. The display according to claim 1 wherein the color filter medium associated with each cell is a colored fluid, the color of the fluid in each cell in a pixel being different from the colors of the fluids in the other cells of the same pixel.

13. The display according to claim 12 wherein there are three cells for each pixel, wherein a first cell includes a red fluid, a second cell includes a green fluid, and a third cell includes a blue fluid.

14. The display according to claim 13 wherein the pigment particles in all of the cells are black.

15. The display according to claim 13 wherein the pigment particles in the cell having the red fluid are cyan, the pigment particles in the cell having the green fluid are magenta, and the pigment particles in the cell having the blue fluid are yellow.

16. The display according to claim 1 further comprising a backlight located behind the rear window for passing light through the rear window and the cells to the front window for observation by a viewer of the display.

17. An electrophoretic display comprising:

a light-transmissive rear window;

a light-transmissive front window;

a plurality of cells located between the rear and front windows, each cell containing charged light-absorbing black pigment particles in a light-transmissive fluid, and wherein laterally adjacent cells are grouped together in threes to form multicolor pixels;

a collecting electrode and a counter electrode associated with each cell, the electrodes being substantially non-obstructive to light and electrically cooperative with one another for removing pigment particles in the cells from the path of light and collecting them on the collecting electrode substantially out of the path of light when the rear window is illuminated from behind so that light can reach the front window without significant attenuation, and for dispersing the pigment particles generally uniformly throughout the fluid in the cells to substantially block the path of light when the rear window is illuminated from behind so that the light is significantly attenuated before reaching the front window;

a red filter element associated with a first cell of each pixel, a green filter element associated with a second cell of each pixel, and a blue filter element associated with a third cell of each pixel; and

a backlight located behind the rear window for passing light through the rear window and the cells to the front window for observation by a viewer of the display.

18. The display according to claim 17 wherein each filter element is located between the respective cell and the front window.

19. The display according to claim 17 wherein each filter element is located within the front window.

20. The display according to claim 17 wherein each filter element is located on the front surface of the front window.

21. The display according to claim 17 wherein each filter element is located between the respective cell and the rear window.

22. The display according to claim 17 wherein each filter element is located within the rear window.

23. The display according to claim 17 wherein each filter element is located on the outer surface of the rear window.