Color Heilmeier displays

For monochrome applications, one can either put a monochrome color filter inside the cell or use monochromatic back-lighting. For Heilmeier displays, there is another way to get a monochrome display by using monochromatic pleochroic dyes [26]. For full-color display, color filters must be used. Heilmeier displays exhibit better color performance than TN displays, as the chroma-ticity of the pixels does not change much at large viewing angles. 

Electric fields have been used to switch a cholesteric texture between the planar, the focal conic, and the homeotropic state. The planar and focal conic states persist after the field is turned off, the choice determined by the amplitude and frequency of the applied field and the rate at which it is turned off. These textural transitions were discovered by Heilmeier and Goldmacher [32] and are used today for color display panels that exhibit gray-scale memory [33,34]. 

Recently, Ong [126] proposed a Heilmei-er display having two asymmetric cells. This display has a high contrast and wide viewing angles, but low transmission. One can also use two separate Heilmeier cells with different dyes to make a composite cell, and by controlling voltage differently a set of colors can be obtained. Two cells with different dyes and one polarizer, can also be used. 

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