Woo-Sang Park

P-95: Electro-Optical Analysis of Super-IPS LCDs by Using 3-D Molecular Director Simulation of TFT-LCDs

In this study, we performed a three-dimensional computer simulation for the electro-optical characteristics of a super in-plane switching liquid crystal displays(Super IPS-LCDs) in a unit pixel of TFT-LCDs, for the first time, and compared the results with experiments. The dynamic equation of continuum theory for liquid crystals is based on a tensorial formulation. As a numerical technique, we used a finite difference method(FDM) suitable for highly nonlinear equations. As a result, we confirmed that the simulation results such as a transmission profile over a pixel and an average transmittance as a function of applied voltage showed good agreement with the experimental results. We also revealed that Super IPS-LCDs show good wide viewing angle characteristics with contrast ratio of more than 50:1 up to a polar angle of ±90° both in the horizontal and the vertical directions.

Optical Compensation of IPS-LCD for Symmetric-High-Contrast at Off-Axis Oblique View

In this study, we proposed an optical compensation method to improve the symmetricity of contrast ratio for wide viewing angle IPS (in-plane switching) LCD. First, the phase retardation depending on the thickness of compensation film is calculated, and then the phase change is presented at the sphere. The phase retardation and the polarization state of the light passing through the optical elements are caculated by using the EJMM (extended Jones matrix method). In addition, the transmittance and the contrast countour are also calculated by using the Berremann`s matrix method. The simulation is carried out for a IPS LC cell with positive A/C/A compensation film. From the standard deviation of the contrast ratio, we confirmed the symmetricity at each viewing angle is inversely proportional to the standard deviation and calculated the optimum design condition of the uniaxial compensation film for the IPS LCD.

Three-Dimensional Analysis of the Autostereoscopic Display with an Array of Lenticulars

Three-dimensional analysis of the optical functionalities of an autostereoscopic display with an array of slanted lenticular lenses was performed. The specification parameters of the lenticular lens for clear separation of the images were first determined using the geometrical optics, and the transmission characteristics of the light ray travelling through a single lenticular were then calculated by finite ray tracing. The properties of light transmission over the entire display panel were then determined by expanding the results obtained for the single lenticular to the entire lenticular lens array. Consequently, each view was confirmed to be located at an inter-ocular distance of 65 mm away from each other. Approximately 5% noise was observed between the views, and the shape of the viewing zone at the optimal viewing distance was tilted towards the direction of the slanted lenticular. Overall, numerical analysis enables a realistic evaluation of the optical functionalities, such as the shape of the viewing zone, of lenticular based autostereoscopic displays.

Optical Analysis for the 3D Display with a Lenticular Array

We propose a generic method to calculate the optical functionalities of a 3D display with a lenticular lens array. In the present work, based on the geometrical optics, it is designed considering the specifications of the display panel. For the effective simulation, we first calculate the optical functionalities of a single cylindrical lens and, by comparing with the results obtained from the conventional geometrical optics, confirm the validity of the present method. Afterwards, we obtain the full distribution of the light intensity at an optimum viewing distance by expanding the results of the single lens to the horizontal plane of the display panel. From these results, we finally confirm whether the 3D images are realized or not in the system.

Theoretical Analysis of Biaxial Films for the Optical Compensation of TN-LCDs

In this paper, we have studied on the optimal design of the optical compensation film for the TN-LCDs. To have wide viewing angle panels, several methods such as multi-domain method, optical path method, and phase compensation method have been proposed. Among these methods, this paper focused on the phase compensation method. In the phase compensation method, the phase retardation generated from the optical birefringence for the off-axis incident is compensated by using optical films with refractive anisotropy. To compensate the phase retardation of the TN-LCDs, we have proposed design concept for the biaxial optical films and analyzed the optical performance for the proposed structures. The calculation of the dynamic motion of the liquid crystals was based on the Ericksen-Leslie theory and the optical performance of the TN-LCD was calculated from the Extended Jones Matrix Method. From the results, we have confirmed that the optical characteristics of the TN-LCDs with the biaxial films have been improved considerably compared with the TN-LCDs compensated by the combination of the uniaxial films.

Improvement of Electrode Structure of FFS Mode LCD for Obtaining High Transmittance

In this study, we proposed a novel electrode structure for the fringe field switching (FFS) mode LCD and performed a three-dimensional computer simulation to calculate the optical transmittance for the new structure. In the simulation Erickson-leslie equation and Berreman matrix were used for obtaining the director distribution profiles of liquid crystal molecules and the electro-optical characteristics, respectively. Considering the complexity of the motional equation of the liquid crystal molecules, FDM (finite difference method) was used as a numerical method. From the results, We revealed that the light transmission of the newly designed pixel structure is expended to the edge of the pixel electrode. We also confirmed that the light transmittance increased more than 13% compared to that of the conventional electrode structure.

LCD Backlighting Systems with a High Luminance and a Good Uniformity

Abstract We performed a 3-dimensional Monte Carlo simulation based on the Mie light scattering theory to investigate the photometric properties of a scattering polymer type light guide, that is known to give a very good brightness. The results reveal that the uniformity of the light guide with polymer scatterers abruptly decreases as the length of the light guide becomes larger than 20 cm. To improve the uniformity of the light guide, we employed a wedge-shaped light guide with dot patterns along with polymer scatterers. As a result, we were able to obtain a backlighting system satisfying a good uniformity and a high luminance at the same time.

Improvement of the Electro-Optical Properties of Film-Type Low Twisted Nematic Liquid Crystal Displays

Abstract We calculated the electro-optical characteristics of FLTN-LCDs using computer simulation of the dynamic behavior of liquid crystal molecules. Through the numerical calculation, it was clarified that the response time of the FLTN-LCDs is about 3 times faster than that of usual TN-LCDs when the identical cell gap is employed. To improve the other electro-optical characteristics, we determined a twisting angle to be about 60° from the view point of an inherent colorization and a gray scale capability and then optimized the material and design parameters of the FLTN-LCDs for the twisting angle of 60°. Under the optimized conditions, we were able to obtain FLTN-LCDs with a fast response time, a good gray-scale capability, a negligible inherent colorization, a high contrast ratio and a wide viewing angle.