Display

Abstract

A display cell having a recorded image includes: a first cell wall; a second cell wall opposed to the first cell wall; and a layer of a display medium disposed between the cell walls. The display medium includes a liquid crystal material having finely-divided pigment particles dispersed therein. Each cell wall includes an electrode for applying an electric field across the display medium. The image includes first picture elements in which pigment particles are aggregated at the first cell wall and second picture elements where the pigment particles are substantially not present at the first cell wall, each first picture element having at least one different light-reflecting property than each second picture element.

1 . A display cell having a recorded image, the display cell comprising:
 a first cell wall;   a second cell wall opposed to the first cell wall;   a layer of a display medium disposed between the cell walls;   the display medium comprising a liquid crystal material having finely-divided pigment particles dispersed therein;   each cell wall including an electrode for applying an electric field across the display medium;   wherein the image comprises first picture elements in which pigment particles are aggregated at the first cell wall and second picture elements where the pigment particles are substantially not present at the first cell wall, each first picture element having at least one different light-reflecting property than each second picture element.   
     
     
         2 . A display cell according to  claim 1 , wherein the liquid crystal material has a dark dye dissolved therein and wherein the pigment particles are light-coloured so that the second picture elements appear dark relative to the first picture elements when the display is viewed through the first cell wall. 
     
     
         3 . A display cell according to  claim 1 , wherein at least one region of the display cell within which opposed electrodes overlap contains both a first picture element and a second picture element. 
     
     
         4 . A display cell according to  claim 1 , wherein each cell wall has only a single electrode which covers substantially all of the area of the cell wall. 
     
     
         5 . A display cell according to  claim 1 , wherein the pigment particles have sizes substantially in the range 100-500 nm. 
     
     
         6 . A display cell according to  claim 1 , wherein the liquid crystal material is a nematic liquid crystal and wherein at least one of the cell walls is provided with a surface alignment to induce local homeotropic alignment of the liquid crystal. 
     
     
         7 . A display cell according to  claim 6 , wherein the first cell wall is provided with the surface alignment.