Effects of Electrode Structure and Electrode Thickness on Flicker in Fringe Field Switching Liquid Crystal Display

• Main Authors: Shueh-Luen Liao, 廖學倫
• Other Authors: Wing-Kit Choi
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/m3wkp2

碩士 === 國立臺灣大學 === 光電工程學研究所 === 107 === In today’s liquid crystal display, TN (Twist Nematic),VA (Vertical Alignment) and IPS(In-Plane Switching) are the most common LCD panel technologies, and all of the above technologies have their pros and cons. This thesis is based on FFS (Fringe-Field Switching) technology, which can improve the light efficiency of original IPS technology. In recent years, active research has been carried out on reducing energy consumption, which however can lead to flicker problem when we use low frequency driving. FFS technology has been used widely in small-size mobile devices such as mobile phone or notebooks. This mode is different from other display such as TV. This is because, for these small mobile touch-screen devices, there will be no touch interference pattern when we use driving technologies that are based on horizontal switching such as IPS and FFS. Unlike dynamic display such as watching movies and animations that require high frequency driving, static image requires only low frequency driving, which can help save power and extend the longevity of device. In this thesis, we investigate the flicker problem in FFS technology driven at low frequency. In the first part of this study, we use different electrode widths and electrode gap to obtain the minimum flickering. By observing the liquid crystal maximum tilt angle, minimum azimuth angle and also the electric field distribution, we can analyze liquid crystal distribution caused by flexoelectric effect. From the results we found that that when the electrode width is smaller, liquid crystal’s maximum tilt angle and minimum azimuth angle can be affected by the electrode gap more seriously. By using the corresponding splay and bend maximum tilt angles, we can obtain the electrode gap values for the minimum flicker to occur for different electrode widths. In the second part of this study, we simulate different electrode thickness. In order to maintain the same cell gap throughout the whole structure, we adopt a planarized structure, which is achieved by adding an insulator layer between the electrodes. From the results, we found that the changing of electrode thickness mainly affects the distribution of liquid crystal molecules above the electrode, the liquid crystal molecules above the middle of the two electrodes are hardly affected by the changing of electrode thickness. Finally, the result shows flicker is least when the electrode thickness is limited to at most 0.15 um.