Cumulative two phase drive scheme for bistable cholesteric reflective displays

A method of addressing a cell of bistable chiral nematic liquid crystal material disposed between opposed substrates, wherein one of the substrates has a plurality of row electrodes facing a plurality of column electrodes on the other substrate, wherein intersections of the row and the column electrodes form a plurality of pixels on the cell, and wherein the bistable chiral netmatic liquid crystal material may be driven to a focal conic texture having a low reflectance, a planar texture having a high reflectance or a combination of the focal conic and planar textures having a gray scale reflectance anywhere between the high and low reflectances, the method comprising the steps of:

• applying a preparation voltage to one of said row electrodes and said column electrodes with the liquid crystal material in either the focal conic texture, the planar texture, or a combination of the focal conic and planar textures to partially drive the liquid crystal material toward the focal conic texture with some of the liquid crystal material remaining in the planar texture unless a complete focal conic texture is desired;
• applying a portion of a selection voltage to one of said row electrodes and said column electrodes while applying a remaining portion of said selection voltage to the other of said row electrodes and said column electrodes;
• allowing the material to relax for a predetermined period of time;
• and
• repeating said applying and said allowing steps until the material is driven to a desired reflectance anywhere between the low reflectance and the high reflectance, wherein the low reflectance is attributable to the material being exclusive in the focal conic texture, the high reflectance is attributable to the material being exclusively in the planar texture, and wherein the reflectance between the high and the low reflectance is attributable to a proportional combination of the focal conic and the planar textures.