Electro-optical properties of twisted nematic liquid crystals : An application to voltage controllable color formation

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Abstract
Optimum conditions for the voltage controllable color formation (VCCF) using nematic liquid crystals with a positive dielectric anisotropy which have homogeneous alignment were studied. It is shown that the optimum condition is realized by choosing the twisting angle of the nematic liquid crystals equal to zero and by setting parallel or crossed polarizers at 45° relative to the directors of the molecules of the liquid crystals. There are several alternative conditions for VCCF. The polarizers used in the research were neutral color polarizers. Spectra of the transmitted light under the application of the voltages were obtained. From the effective birefringence, the widths of the spectra were determined. These values are compared with those which were determined by an independent method. Good agreement between them shows a validity of the model adopted in this work