1 Improved PVA LC Cell using Strong Fringe Field Effect for Fast response time Seung-Hoon Ji *, Yong-Hyun Choi *, Jung-Hee Son * and Gi-Dong Lee * * Department of Electronics Engineering, Dong-A University, Busan , Korea

2 ▷ Introduction ▷ Conventional PVA LC cell -. Characteristics of transmittance and director motion ▷ Proposed PVA LC cell -. New electrode structure -. Optical transmittance and iso-potential line -. Enhancement of response time ▷ Conclusion Contents

3 Especially, we focus on improving response time of the PVA LC mode. Introduction Issue Point 1. High Display Image Quality -. Wide Viewing angle for family use Fast response time for moving picture -. Fast response time for moving picture -. High contrast ratio / High brightness 2. Lower Power consumption 3. Cost Competitiveness ▣ Design issues of TFT-LCD TV Various LC modes PVA such as PVA, MVA, IPS, FFS, OCB are developed.

4 ▣ Characteristics of the conventional PVA LC cell (a) Black state of the PVA LC cell (b) Schematic cross-sectional structure of the cell along A-B and LC director distribution A B Polarizer Analyzer AB Common electrode Glass Alignment layer VA LC Pixel electrode Glass Alignment layer Slit Non rubbing process is suitable for the large-sized application. Merit off state Conventional PVA LC cell

5 (a) White state of the PVA LC cell (b) Schematic cross-sectional structure of the cell along A-B and LC director distribution A B Polarizer Analyzer B Non rubbing process also deteriorates response time of the PVA LC cell. Demerit Common electrode Glass Alignment layer VA LC Pixel electrode Glass Alignment layer A ▣ Characteristics of the conventional PVA LC cell on state Conventional PVA LC cell

6 ▣ Electrode structure of the proposed PVA LC cell Top Bottom Fringe field electrode (V f ) Dielectric layer Z X Common electrode (V com ) Pixel electrode (V pixel ) Proposed conceptExpected effects Applying Fringe field electrode to the conventional structure 1. Improvement of director orientation 2. Fast response time Proposed PVA LC cell

7 ▣ Optical transmittance – at 2 msec (pre-tilt angle = 89° ~ 91°) (a) Conventional structure (b) Proposed structure We can see that the optical transmittance on the slit increases due to the increased strong fringe field. Analysis Y X 2ms 10V 5V Time Voltage V com V pixel V f Simulated by TechWiz LCD Proposed PVA LC cell

8 ▣ Iso-potential line and LC distribution – at 2 msec Increased strong fringe field on the slit helps LC director in the bulk area to have appropriate orientation quicker than before. Analysis (a) Conventional structure (b) Proposed structure Fringe field electrode Simulated by TechWiz LCD Z X Proposed PVA LC cell

9 ▣ Calculated response time Conventional PVA LC cell Proposed PVA LC cell Time [msec] Transmittance [a.u.] The fringe field electrode helps LC director field to have a uniform reorientation so that we can get the faster rising time. Analysis Conventional PVA LC cell Proposed PVA LC cell Tr ms ms Tf ms ms Proposed PVA LC cell

10 Conclusion ▣ We propose an improved pattern structure that can reduce the rising time by using strong field in the PVA LCD. ▣ The increased strong fringe field on the edge of the electrode can help the LC director in the bulk area to have an appropriate orientation quickly when we applied voltage. ▣ From the simulation results, the proposed structure exhibited 74.2% improvement in rising time compared to the conventional structure.

11 Introduction ▣ Optical property of the PVA LC cell (a) Black state of the PVA LC cell, (b) schematic cross-sectional structure of the cell along A-B and LC director distribution A B A B Polarizer Analyzer (a)(b)(a)(b) (a) White state of the PVA LC cell, (b) schematic cross-sectional structure of the cell along A-B and LC director distribution Polarizer Analyzer A B A B Slit among the electrodes