The Natural Pitch Effects On Twist Nematic Liquid Display

Twist nematic mode liquid crystal displays are widely used. It is mainstream displays because of its low operate voltage, low consumption, long life, more gray, full-color capability characteristics. The conventional twist nematic liquid crystal displays exists a narrow viewing angle and slow response speed. In the last few years, viewing angle has been improved great progress, but the response speed is not improved more that affects the development of twist nematic liquid crystal displays. Thus, improving the response speed based on the very mature technology is an important technical topic for the best display effect.The parameters of liquid crystal displays device influence response time are: cell thickness (d), the rotation viscosity coefficient (γ) and elastic constants (K). There has a relationship between the response time and the natural pitch from some experiments.The influence of the natural pitch is slightly different for the LCD with different twist angle.In this thesis, we researched the natural pitch effects on twist nemaic liquid crystal display and vertically aligned twist nemaic liquid crystal display. The natural pitch effects on threshold voltage and the response time were theoretically studied in twist nemaic liquid crystal display and the vertically aligned twist nematic liquid crystal display. Based on theoretical analysis, the relationship of the natural pitch and the response time is obtained. Using simulation software, the response time, the electro-optic properties, iso-transmittance contour of the dark states, iso-transmittance contour of the bright states and iso-CR contour of the normal white twisted nemaic liquid crystal display and vertically aligned-twisted nemaic liquid crystal display with different twist angle and different the natural pitch were numerically simulated, compared and analyzed. The display properties of LCD were improved through considering the twist angle and the natural pitch together.