Improvement of contrast ratio of reflective cholesteric liquid crystal displays

Reflective cholesteric liquid crystal (CLC) displays with bistability has been bepaid much attention recently, and the products, such as electronic books, notebooks, electronic papers, digital billboards, and others, having several sizes havebeen developed. However, the brightness of a reflective display depends on theambient light and its structures. To get higher contrast ratio of a reflective display,the high and low reflections for bright and dark states, respectively, should beobtained. In this proposal, the main topic is to improve the contrast ratio ofreflective CLC displays based on the reduction of light leakage of dark state. Theapproaches will be adopted to increase the contrast ratio. The first one is toreduce the light leakage at dark states of focal conic textures, indicating that thebackward (forward) scattering should be reduced (increased). According to theelectrohydrodynamic effect, impurities will be doped into CLCs to change thedomain size of focal conic textures, so the scattering phenomenon will bemodified. Additionally, the polymer surface structures will also affect the domainsize of focal conic textures. The other approach is to generate uniform lying helix(ULH) structures having high transmission to replace the dark state of the currentCLC displays, i.e. focal conic textures. It should be noted that the formation ofULH structures via electric driving at room temperature is challenged. Here, theULH structures, planar textures, and focal conic textures, will be tried togenerated by material preparations and polymer stabilizations to apply to thethree stable states of CLC displays. The purpose of the methods describedabove is to enhance the contrast ratio of CLC displays.