Eung-Sang Lee

A study on reducing image‐sticking artifacts in wide‐screen TFT‐LCD monitors

— In order to improve the image quality of flat-panel displays, the image retention of a display has to be reduced. But at the same time, display devices also have to produce durable images while they are used for long periods of time in a single session. To achieve high-quality images with reduced image sticking in TFT-LCD devices, we have increased their voltage-holding ratio (VHR). This technology ensures the achievement of durable images over long periods of time and also reduces the image-sticking problem. There are many ways to achieve increased VHR. In terms of the characteristics of the TFT devices, reducing the leakage-current effects is the most frequently applied method in the display industry.

55.4: Design of Integrated a-Si Gate Driver Circuits for Low Power Consumption

We have developed integrated a-Si:H TFT gate driver circuits on large area TFT-LCD for low power solution. The proposed driving scheme achieves 40% lower power consumption than that of a conventional a-Si:H TFT gate drivers by means of double 2-phase clock system. We have redesigned a-Si:H gate driver circuit and made the proto type 13.3″WXGA panel.

P-54: The Charging Difference Minimization of the Physically Divided A-Si TFT LCD Panel for Dual Scanning

In this paper, we describe a driving method to overcome the charging difference at the physically divided TFT- LCD panels. The charging difference causes a line at the center of the panels. To reduce the above effect, the upper half of the TFT-LCD panel is driven sequentially from the middle horizontal line to the first line and the bottom half is driven from the middle horizontal line to the last line. Furthermore we implement a horizontal line skew driving method between upper and lower panel driving, which removes the abnormal charging at the middle horizontal line caused by parasitic capacitance effects. By using the above two methods simultaneously, one can acquire good quality pictures on a 28.0 inch (2048X2048) panels.

Effect of liquid crystal elastic constants on the matrix-addressed operation of a bistable twisted-nematic liquid crystal display

A bistable twisted nematic (BTN) LCD exhibits optical bistability, fast response time, high contrast, and wide viewing angle. For high speed operation of a high resolution BTN panel without any cross-talk problem, the drive scheme must be optimized for matrix addressing. In our previous works, we introduced a high speed addressing method and a method for the optimization of the drive scheme for matrix-addressed operation of a BTN LCD. In this work, we introduce the optimization method of drive scheme by using a weighting function and studied dependence of the weighting function of a BTN LCD on elastic constants of liquid crystal.

Analysis and design of a multicolor STN-LCD on the Poincaré sphere

A multicolor STN-LCD based on the electrical control of birefringence was analyzed and designed on the Poincare sphere. The optical conditions of the cell were chosen from the Poincare sphere. A retardation film provides brighter white, red, blue, and green colors within a small applied-voltage variation. Experimental results show good agreement with numerical calculations.