52.2: High‐Speed Bend Transition Method using Electrical Twist Field in OCB Mode TFT‐LCDs

Abstract

We have developed high‐speed bend transition method of OCB (Optically Compensated Bend) mode TFT‐LCDs. We found out that nucleation of bend transition occurs with twist alignment. New pixel structure and driving scheme generate bend domains using “electrical twist field” which is lateral electric field to induce twist orientation of liquid crystal. The probability of bend nucleation depends on lateral twist and vertical transition electric field, and slightly depends on temperature. Growth speed of bend domain depends on the vertical transition voltage and viscosity of the liquid crystal. Bend transition time is mainly determined by the growth speed. A lower viscosity liquid crystal and a high transition voltage are preferable to achieve the high‐speed bend transition especially at low temperature. We have developed 22 inch diagonal HDTV which achieved the bend transition time to be less than 0.2 sec even at 0°C

Color Sequential Mobile LCDs

“…Unlike conventional homogeneous cells, in a pi-cell, the surface pre-tilt angles are in a parallel direction, as shown in Figure 5.4. There have been numerous successful efforts to develop methods that could speed up this initial 'splay to bend' transition and maintain the bend orientation even at a low voltage, such as using polymer network formation [20][21][22][23], high surface pre-tilt angle [24,25], or special driving schemes and fields with irregular electrode layouts [26,27]. As the voltage increases above the critical voltage, certain nuclei will be generated near the surface and propagate towards the bulk region to transform the alignment into a low bend state.…”

Analysis of electro‐optical properties of polymer‐stabilized OCB and the application to TFT‐LCDs

“…OCB (optically compensated bend) mode 1 based on the Pi-cell structure 2 has great advantages of fast response and wide viewing angle. However, the OCB mode requires a transition of liquid crystals from an initial splay state to a bend state 3 .…”

62.4: Development of Zigzag Thin‐Film‐Transistor‐Driven OCB for Field‐Sequential‐Color LCDs with High Aperture Ratio

“…Field-sequential color (FSC) display [3][4][5][6][7] without the color-filterformed sub-pixels is supposed to be the best approach to achieve high panel transmittance. However, it is still difficult to design an a-Si TFT pixel with high aperture ratio (HAR) without the usage of a thick organic layer on the TFT-substrate.…”