Masuyuki Ohta

Complete Suppression of Color Shift in In-plane Switching Mode Liquid Crystal Displays with a Multidomain Structure Obtained by Unidirectional Rubbing

Complete suppression of color shift in in-plane switching mode liquid crystal displays (LCDs) has been realized. The LCDs have a multidomain structure obtained by unidirectional rubbing and use of zigzag electrodes. The design concept and performance of the devices are described in this paper.

18.4: Development of a 19-in.-diagonal UXGA Super TFT-LCM Applied with Super-IPS Technology

A 19-inch diagonal UXGA TFT-LCM with a mega wide viewing angle applied with Super-IPS technology has been developed. A high aperture ratio which is the same as that of the current 18.1- inch SXGA LCM under UXGA resolution in the 19-inch diagonal LCM was obtained by optimization of pixel structure and the development of a liquid crystal mixture with low driving voltage. Introducing a compensatory pixel structure solved the problem of non-uniformity of the brightness caused by signal delay. Moreover, the same external dimensions as those of the current 18.1-inch TFT-LCM and thinner package were realized.

Dependence of viewing angle characteristics on pretilt angle in the in-plane switching mode

Viewing angle characteristics were systematically obtained when using in-plane switching (IPS) of liquid crystals. Although the IPS mode originally shows stable electro-optical performance regardless of viewing directions, the viewing angle characteristics are found to be strongly dependent on pretilt angle (slant angle of the liquid crystals from the substrate). Experimentally, the smaller the pretilt angle of the liquid crystal, the much wider the viewing angle characteristics, while larger pretilt angles of liquid crystals cause the characteristics to deteriorate. This deterioration occurs in a particular viewing direction, i.e. at right angles to the initial orientation direction of the liquid crystal when there is no in-plane electric field. The experimentally observed behaviour of the viewing angle dependence on the pretilt angle was also confirmed by computer simulations. Calculated iso-contrast contour lines, as a function of the pretilt angles, nearly coincide with the experimentally obtained vie...

10.1: 18.0-in.-Diagonal Super-TFTs with a Fast Response Speed of 25 msec

Materials and components available for the mass production of Super-TFTs IPS-TFT-LCDS were optimized and redesigned on the basis of a fundamental analysis of the IPS mode. As a result, we developed 18.0-inch diagonal Super-TFTs with a fast response speed of 25 msec., which is the total on +off response time between white and black levels. Moreover, we found that the IPS mode has a relatively higher potential for displaying a moving gray level image compared with that of the conventional TN-mode.

Unusual Voltage-Holding Ratio Characteristics Using In-Plane Switching of Nematic Liquid Crystals

Unusual characteristics of the voltage-holding ratio were found when using in-plane switching of homogeneously oriented nematic liquid crystals. Even when employing liquid crystals with much lower resistivity than is applicable to the conventional active matrix driving technique, voltage-holding ratio characteristics were higher than those in conventional electric fields applied along the direction perpendicular to the substrate plane. The unusual holding ratio characteristics were attributed to the electric field direction being approximately parallel to the substrate plane.

Physical behavior of nematic liquid crystals using the in-plane switching mode

Abstract We have investigated the switching and response mechanism of the in-plane switching (IPS) mode which is a novel technique for wide viewing-angle liquid crystal displays. In the IPS mode, an in-plane electric field is applied to the liquid crystals along the direction parallel to the plane of the substrates. First, it was made clear that it was the electric field and not the voltage that drove the liquid crystals in the IPS mode. An inversely proportional relationship between the threshold voltage and the cell gap was found to hold. Second, the relaxation time of the liquid crystals when removing the electric field was described as a proportional relationship to the square of cell gap. A thinner cell gap also proved to be effective to obtain fast response time in the IPS mode. In contrast, the electric field strength governed the switching-on time when applying the in-plane electric field.

A robust design against comb electrode spacing variations for in-plane switching mode thin-film transistor liquid-crystal displays

A method to reduce the transmittance nonuniformity caused by comb electrode spacing variations of in-plane switching mode thin-film transistor liquid-crystal displays is proposed. The method is based on the compensation of the effect of the comb electrode spacing variations with effective driving voltage variation via feed-through voltage in the thin-film transistor addressing. The conditions for this compensation were analyzed theoretically taking into account gate delay (recharging) effects. It was observed that the common dc driving was superior to the common inversion driving in terms of compensation efficiency. An alternative driving method was proposed to enhance the compensation in common inversion driving.

Performance optimization of in-plane switching AM-LCDs by using systematic device simulations

Electro-optical performances of in-plane switching mode active matrix addressed liquid crystal (LC) displays were analyzed by using device simulations. Practical combinations of 2D simulations to analyze precise electric and LC director fields and fast 1D simulations to grasp electro- optical characteristics were systematically utilized. Electrode geometries and tilt angle of the LC molecules at the substrate surface were identified as key points to optimize the electronic performance and optical performance, respectively.