Gak Seok Lee, Jae Chang Kim, and Tae-Hoon Yoon

Department of Electronics Engineering, Pusan National University, Busan, 609-735 Korea

As the high quality of display is in great demand, wide-viewing angle also became one of necessary characteristics in transflective LCDs. Among conventional LC modes, VA and IPS modes are the powerful candidates for wide-viewing angle display. Many attempts to apply these two modes to transflective LCDs have been reported. In application of the IPS mode to transflective LCDs, it is very difficult to realize the reflective part, because LC layer under a quarter-wave plate always has the retardation effect regardless of the applied electric field. On the contrary, LC layer in VA mode has no retardation originally, but it can have retardation effect with the applied electric field. In this paper, we propose a vertically-aligned transflective LC cell driven by the lateral electric field. In contrast to the conventional VA mode, liquid crystal material with positive dielectric anisotropy is used to realign them parallel to the applied lateral electric field. Because retardation of the reflective part should be a half of the transmissive part, the intensity of the electric field in the former should be smaller than that in the latter. To reduce the intensity of the electric field applied to LC layer, an organic layer is inserted between LC layer and ITO in the reflective part, which is called the cap-dividing method.[1] However, the threshold voltage of the reflective part becomes higher than that of the transmissive part. In the inter-digital electrode structure, the threshold voltages can be controlled by adjusting the ratio of electrode width and the distance between electrodes.[2] In short, with optimizing the electrode structure and by using the cap-dividing method, single gamma curve can be achieved as shown in Fig. 1.

References [1] S.-G. Kang, S.-H. Kim, S.-C. Song, W.-S. Park, C. Yi, C.-W. Kim, and K.-H. Chung, SID 2004 Digest, pp. 31-33. [2] G. S. Lee, J. C. Kim, and T.-H. Yoon, Proc. Int'l Meeting of Information Display 2006.

Fig. 1. Electro-optic characteristics of a vertically-aligned transflective LC cell with the optimized electrode structure.