Optimal Design of the Edge Structure of a Pixel Electrode for Improving Transmittance of the Fringe Field Switching (FFS) Mode LCDs

초록

In this study, we proposed a method to design optimally the edge structure of a pixel electrode of the fringe field switching liquid crystal displays (FFS-LCDs) to obtain stable behavior of liquid crystal molecules and high transmittance around the edge of a pixel[1]. The edge part of a pixel electrode was divided into 4 regions. Each region was defined not to show reverse twist of liquid crystal molecules leading to dark area for applied electric field. To verify the effect of the optimally designed edge structure, we performed numerical simulation using commercially available 3-demensional simulator. The simulation was performed according to the variation of the inclination angle of a slit between pixel electrodes which was expected to exert an effect on the formation of electric field around the edge of a pixel electrode. As a result, it was confirmed that homogeneous orientation of liquid crystal molecules could be obtained without any reverse twist over the whole area of the edge of a pixel electrode. It was also revealed that symmetrical electric field disappeared around the edge of a pixel and dark lines could be hardly observed. Therefore, the transmittance of a pixel with optimally designed edge structure was higher than that of the conventional structure, even if the difference in transmittance between the optimally designed edge structure and the conventional one varies with the inclination angle of the slit. Consequently, comparing optimally designed edge structure with the conventional one, the transmittances of optimally designed structures with the slit inclination of 7° and 3° were increased by 27% from 10.6% to 13.5% and 16% from 12.0% to 14.0% at the edge of a pixel electrode, respectively (Fig. 1). As for the whole area of a pixel, the transmittance was improved by 6.9% from 22.8% to 24.8% for the slit inclination of 7° and 6.1% from 23.7% to 25.2% for the slit inclination of 3° (Fig. 2).