Cholesteric texture displays, polymer

Electro-Optic Properties of Polymer Stabilized Liquid Crystals. Polymer networks have been used to stabilize many of the liquid crystal display states in various types of displays quite advantageously. In this section, we present some recent work on correlating the material properties of the liquid crystal/polymer network composite to the electro-optic properties of the flat-panel displays specifically cholesteric texture displays (75) and simple nematic birefringent type displays (7(5). 

Nematic gels are very interesting systems, thus deserving further study. Actually, these systems are being studied experimentally for applications. Examples are polymer dispersed liquid crystal displays are sometimes dispersed not in a polymer, but in a polymer network. Displays by means of the polymer stabilized cholesteric texture change, are also achieved in crosslinked systems. In addition, the chiral smectic phase has been obtained in such systems as well. Other types of liquid crystal gels have been applied or are expected to be applied in such devices. 

Polymer-dispersed LC (PDLC) [30], polymer-stabilized cholesteric texture (PSCT) [31], and LC gels [32] all exhibit optical scattering characteristics and have wide applications in displays and optical devices. The LC gel-based reflective LCD can also be extended to transflective... 

J. W. Doane, D.-K. Yang, and Z. Yaniv, Front-lit flat panel display from polymer stabilized cholesteric textures, Proc. Japan Display 92, 73 (1992). 

Chien and coworkers [68] devised a material scheme to manufacture red, green, and blue pixels of polymer-stabilized cholesteric textures by selectively adjusting the chiral pitch length spatially across the display substrate using... 

Cholesteric polyesters were prepared from silylated derivatives of 2,3-di-(9-isopropylidene-D-threitol, DAS, or DAM with dicarboxylic acid dichlorides by polycondensation in solution [34]. Trifluoroacetic acid-water allowed an easy cleavage of the isopropylidene group without hydrolysis of the polyester. All these polyesters formed a broad cholesteric phase, and the polymers containing 5 or 10 mol per cent sugar diol displayed a blue Grandjean texture. 

Figure 10.23 The reflection spectra of the cholesteric displays. P planar texture, F focal conic texture, (a) The regular polymer stabilized cholesteric display, and (b) The polymer stabilized black-white display.

In addition to the TN and IPS modes in nematic displays, himdreds of other displays methods were invented and tested over the last 30 years. Out of them the bistable nematic development based on surface flexoelectric interactions, the bistable cholesterics displays based on switching between planar and focal conic textures and the polymer dispersed liquid crystal displays found some applications. None of them, however, offer better than a few milliseconds switching time. 

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