Methods for driving bistable electro-optic displays, and apparatus for use therein

Abstract

A bistable electro-optic display has a plurality of pixels, each of which is capable of displaying at least three gray levels. The display is driven by a method comprising: storing a look-up table containing data representing the impulses necessary to convert an initial gray level to a final gray level; storing data representing at least an initial state of each pixel of the display; receiving an input signal representing a desired final state of at least one pixel of the display; and generating an output signal representing the impulse necessary to convert the initial state of said one pixel to the desired final state thereof, as determined from said look-up table. The invention also provides a method for reducing the remnant voltage of an electro-optic display.

1 . A method of driving a bistable electrophoretic display having at least one pixel with two extreme optical states, the method comprising:
 (a) driving the pixel from an initial gray level to one extreme optical state different from the initial gray level; and   (b) driving the pixel from the one extreme optical state to a final gray level different from the one extreme optical state.   
     
     
         2 . A method according to  claim 1  wherein step (b) is effected by driving the pixel from the one extreme optical state to the opposed extreme optical state, thereafter driving the pixel back to the one extreme optical state and thereafter driving the pixel to the final gray level. 
     
     
         3 . A method of driving a bistable electro-optic display having at least one pixel with two extreme optical states, the method comprising:
 (a) driving the pixel from an initial gray level to one extreme optical state different from the initial gray level; and   (b) driving the pixel from the one extreme optical state to a final gray level different from the one extreme optical state,   wherein the display is an encapsulated electrophoretic display comprising a plurality of capsules, each of which itself comprises an internal phase containing electrophoretically-mobile particles suspended in a liquid suspension medium, and a capsule wall surrounding the internal phase.   
     
     
         4 . A method according to  claim 1  wherein the display is a microcell display comprising charged particles and a suspending fluid retained within a plurality of cavities formed in a carrier medium. 
     
     
         5 . A bistable electrophoretic display having at least one pixel with two extreme optical states, and a display controller for applying electric field to the pixel and thereby changing the optical state thereof from an initial gray level to a final gray level, the display controller being arranged to:
 (a) drive the pixel from the initial gray level to one extreme optical state different from the initial gray level; and   (b) drive the pixel from the one extreme optical state to a final gray level different from the one extreme optical state.   
     
     
         6 . A display according to  claim 5  wherein the display controller is arranged to effect (b) by driving the pixel from the one extreme optical state to the opposed extreme optical state, thereafter driving the pixel back to the one extreme optical state and thereafter driving the pixel to the final gray level. 
     
     
         7 . A bistable electro-optic display having at least one pixel with two extreme optical states, and a display controller for applying electric field to the pixel and thereby changing the optical state thereof from an initial gray level to a final gray level, the display controller being arranged to:
 (a) drive the pixel from the initial gray level to one extreme optical state different from the initial gray level; and   (b) drive the pixel from the one extreme optical state to a final gray level different from the one extreme optical state,   
       wherein the display is an encapsulated electrophoretic display comprising a plurality of capsules, each of which itself comprises an internal phase containing electrophoretically-mobile particles suspended in a liquid suspension medium, and a capsule wall surrounding the internal phase. 
     
     
         8 . A display according to  claim 5  which is a microcell display comprising charged particles and a suspending fluid retained within a plurality of cavities formed in a carrier medium. 
     
     
         9 . A method according to  claim 1  wherein step (b) is effected by driving the pixel from the one extreme optical state to the opposed extreme optical state and thereafter driving the pixel to the final gray level. 
     
     
         10 . A display according to  claim 5  wherein the display controller is arranged to effect (b) by driving the pixel from the one extreme optical state to the opposed extreme optical state and thereafter driving the pixel to the final gray level.