Electrophoretic displays

Abstract

A dielectrophoretic display comprises a substrate having walls defining at least one cavity, the cavity having a viewing surface and a side wall inclined to the viewing surface; a suspending fluid contained within the cavity; a plurality of at least one type of particle suspended within the suspending fluid; and means for applying to the fluid an electric field effective to cause dielectrophoretic movement of the particles to the side wall of the cavity.

1 . A display comprising:
 a substrate having walls defining at least one cavity, the cavity having a viewing surface, a rear surface on the opposed side of the cavity from the viewing surface, and at least one side wall extending between the viewing surface and the rear surface;   a colored fluid contained within the cavity;   a plurality of electrically charged solid particles within the fluid;   a front electrode adjacent the viewing surface of the cavity;   a rear electrode adjacent the rear surface; and   a side electrode adjacent the side wall,   the display having a first optical state in which the solid particles lie adjacent the front electrode, a second optical state in which the solid particles lie adjacent the rear electrode and a third optical state in which the solid particles lie adjacent the side electrode.   
     
     
         2 . A display according to  claim 1  wherein the solid particles are white in color. 
     
     
         3 . A display according to  claim 1  wherein the cavity has a non-circular cross-section as seen from the viewing surface. 
     
     
         4 . A display according to  claim 3  wherein the cavity has a polygonal cross-section as seen from the viewing surface. 
     
     
         5 . A display according to  claim 1  wherein the substrate comprises a substantially rigid material having the at least one cavity formed therein, the substrate further comprising at least one cover member closing the at least one cavity. 
     
     
         6 . A display according to  claim 1  arranged to have light projected on to a surface on the opposed side of the display from the viewing surface. 
     
     
         7 . A process for operating a display, the process comprising:
 providing a substrate having walls defining at least one cavity, the cavity having a viewing surface, a rear surface on the opposed side of the cavity from the viewing surface, and at least one side wall extending between the viewing surface and the rear surface; a colored fluid contained within the cavity; a plurality of electrically charged solid particles within the fluid; a front electrode adjacent the viewing surface of the cavity; a rear electrode adjacent the rear surface; and a side electrode adjacent the side wall; and   applying to the front, rear and side electrodes electrical potentials effective to cause the solid particles fluid to assume:   (a) a first position in which the solid particles lie adjacent the front electrode, and the display shows a first optical state;   (b) a second position in which the solid particles lie adjacent the rear electrode and the display shows a second optical state; and   (c) a third position in which the solid particles lie adjacent the side electrode and the display shows a third optical state.   
     
     
         8 . A process according to  claim 7  wherein the solid particles are white in color. 
     
     
         9 . A process according to  claim 7  wherein the cavity has a non-circular cross-section as seen from the viewing surface. 
     
     
         10 . A process according to  claim 9  wherein the cavity has a polygonal cross-section as seen from the viewing surface. 
     
     
         11 . A process according to  claim 7  wherein the substrate comprises a substantially rigid material having the at least one cavity formed therein, the substrate further comprising at least one cover member closing the at least one cavity. 
     
     
         12 . A process according to  claim 1  further comprising projecting light on to a surface on the opposed side of the display from the viewing surface. 
     
     
         13 . A variable transmission display comprising:
 an electrophoretic medium comprising a fluid and a plurality of electrically charged particles dispersed in the fluid, the electrophoretic medium being capable of assuming a light-transmissive state and a substantially non-light-transmissive state;   at least one light-transmissive first electrode disposed adjacent the electrophoretic medium;   a plurality of light-transmissive second electrodes disposed adjacent the electrophoretic medium on the side thereof remote from the first electrode(s); and   voltage means for varying the potential each of the second electrodes independently of one another.   
     
     
         14 . A variable transmission display according to  claim 13  wherein the second electrodes being arranged in a plurality of rows and a plurality of columns, and the voltage means comprising row and column electrodes connecting the second electrodes in each row and column respectively. 
     
     
         15 . A variable transmission window according to  claim 14  further comprising a transistor associated with each second electrode.