Transmissive electrophoretic display with vertical electrodes

• US 6,144,361 A
• Filed: 09/16/1998
• Issued: 11/07/2000
• 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): Hjerpe, Richard A.
• Assistant Examiner(s): Bowers, Benjamin D.
• Application Number:
  US09/154,364
• Time in Patent Office: 783 Days
• Field of Search: 345/107, 359/296
• US Class Current: 345/107
• CPC Class Codes: G02F 1/167 by electrophoresis
• CPC Class Codes: G02F 1/16761 Side-by-side arrangement of working electrodes and counter-electrodes

Abstract

A transmissive electrophoretic display is generally comprised of a regular lateral array of transmissive electrophoretic cells; each uniformly illuminated from the rear by a backlight. 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, and at least one non-obstructing, vertically-disposed collecting electrode. With the application of appropriate voltages to the collecting and counter electrodes, each cell can be switched between a light and dark state. In the dark state, the light-absorbing pigment particles are distributed to cover the horizontal area of the cell, thus absorbing light from the backlight and preventing it from reaching the viewer. In the light state, the light-absorbing pigment particles are collected on vertical surfaces within the cell, thus allowing light from the backlight to pass through the cell and reach the viewer.

Claims

1. An electrophoretic display comprising:

a generally planar light-transmissive rear window;

a generally planar light-transmissive front window;

a plurality of cells located between the rear and front windows, each cell having a front wall generally parallel to the planar front window, a rear wall generally parallel to the planar rear window, four side walls generally perpendicularly to the rear and front windows and having generally rounded interior corners, and a center post located generally at the center of and extending generally perpendicularly to the planar rear and front windows, and each cell containing charged light-absorbing pigment particles in a light-transmissive fluid;

a collecting electrode within each cell and comprising the four side walls within each cell, the collecting electrode being substantially non-obstructive to light for removing pigment particles in the cells from 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 distributing the pigment particles 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; 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.

2. The display according to claim 1 wherein the center post has a generally rectangular cross section.

3. The display according to claim 1 wherein the counter electrode includes the center post.

4. The display according to claim 1 wherein the collecting electrode includes the center post.

5. The display according to claim 4 wherein each cell has a plurality of side posts extending generally perpendicularly to the planar rear and front windows and located between the center post and the side walls, and wherein the counter electrode includes the side posts.

6. An electrophoretic display comprising:

a generally planar light-transmissive rear window;

a generally planar light-transmissive front window;

a plurality of cells located between the rear and front windows, each cell having a front wall generally parallel to the planar front window, a rear wall generally parallel to the planar rear window, four side walls generally perpendicularly to the rear and front windows and having generally rounded interior corners, and a center post located generally at the center of and extending generally perpendicularly to the planar rear and front windows, and each cell containing charged light-absorbing pigment particles in a light-transmissive fluid; 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;

and wherein the four side walls of each cell form a collecting electrode substantially non-obstructive to light for removing pigment particles in the cells from the path of light when the rear window is illuminated from behind so that light can reach the front window without significant attenuation, and wherein the center post of each cell forms a counter electrode substantially non-obstructive to light and cooperative with the collecting electrode for distributing the pigment particles 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.

7. The display according to claim 6 wherein the center post has a generally rectangular cross section.

8. An electrophoretic display comprising:

a generally planar light-transmissive rear window;

a generally planar light-transmissive front window;

a plurality of cells located between the rear and front windows, each cell having a front wall generally parallel to the planar front window, a rear wall generally parallel to the planar rear window, four side walls generally perpendicularly to the rear and front windows, and three spaced-apart parallel plates oriented generally perpendicularly to the planar rear and front windows, and each cell containing charged light-absorbing pigment particles in a light-transmissive fluid;

a collecting electrode within each cell and comprising the four side walls and the center one of said three plates within said each cell, the collecting electrode being substantially non-obstructive to light for removing pigment particles in the cells from 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 within each cell and comprising the other two of said three plates within said each cell, the counter electrode being substantially non-obstructive to light and cooperative with the collecting electrode for distributing the pigment particles 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; 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.