Tetsuya Satake

Electrooptical Study of an In-Plane Switching Mode Using a Uniaxial Medium Model

A new modeling method using a uniaxial medium model has been proposed to obtain a simple and quantitative expression for the transmittance of an in-plane switching (IPS) mode. In this model, the effective birefringence (Δneff) and the apparent optic axis rotation angle (app) are used instead of the original birefringence and the director profile, and Δneff changes when an electric field is applied to the IPS mode cell. The dependences of Δneff (measured as a retardation) and app on the applied voltage have been evaluated first by experiment. Δneff was reduced to 80% of the original value and app rotated 45° at the maximum transmittance (Tmax). It has been confirmed that the transmittance can be reproduced satisfactorily by employing the models expression using the observed Δneff and app values. Theoretical simulation has also been executed and the results supported the experimental results. The simulation has also shown that both the Δneff–Δn ratio and app at Tmax are almost constant and do not depend on either the cell gap or liquid-crystal properties. Tmax can be easily calculated using the uniaxial medium model.

A new field sequential stereoscopic LCDs by use of dual‐directional‐backlight

Abstract We have developed the Scan‐backlight Stereoscopic LCD that is a kind of field‐sequential ‐Stereoscopic LCD combining the Dual‐ Directional‐ Backlight and the fast‐response OCB panel. The Dual‐Directional‐Backlight using a double‐sided prism sheet can change the direction of light by switching the LED light sources. The OCB panel using Feed‐Forward Drive can realize frame rate of 120 Hz. As a result, the Scan‐backlight Stereoscopic display works at its original resolving power, and produces flicker‐free stereoscopic images. This auto‐ stereoscopic display can resolved the problems of the double images and the pseudoscopic images in case of watching at oblique angles.

53.2: A Novel Optical System LED-Backlight with Excellent Brightness Uniformity for TFT-LCD

We have developed a new LED-backlight structure. By applying this new structure to a 12.1-inch SVGA TFT-LCD, the number of LEDs can be reduced approximately 60% compared with the conventional structure while keeping the same level of brightness uniformity.

Simple Method of Measuring Alignment Directions and Retardation of Liquid Crystal Cells

We developed a simple method of measuring alignment directions and retardation of twisted nematic liquid crystal cells. Our method is particularly suitable for the distribution measurement of such cell parameters of the in-plane switching and fringe-field switching panels. The normalized Stokes parameters of light passing through the cell, i.e., S1 and S2, show a special property wherein a point of (S1,S2) in the S1–S2 plane of the Poincare sphere moves on a circle by rotating the cell. A twist angle and retardation of the cell can be evaluated from the center of the circle separately from an alignment direction at a substrate interface. The alignment direction at the substrate interface can be evaluated by explicit calculation using the evaluated twist angle and an angle between the S1-axis and a line from the center of the circle to the point of (S1,S2).

Cell-Gap Measurement of Reflective Twisted-Nematic Liquid Crystal Display with Internal Surface-Roughened Reflector

A new cell-gap measurement method is described for reflective twisted-nematic liquid crystal displays (TN-LCDs). The behavior of reflected-light intensity in the cell-gap measurement shows that the surface reflection of the display has a decisive influence on the obtained cell gap. The new measurement method, which takes into account the surface reflection, exhibits a good cell-gap agreement with a transmissive cell-gap measurement in an experiment using transmissive LC cells and an external reflector. Signal reflected-light intensity depends on the measurement point in the case of a display having a surface-roughened reflector. The signal becomes smaller on the slant face than both at the top and bottom of the reflector. Correction for signal variation is also included in the new method. The method is applied to microscopic cell-gap mapping using a microscope and a charge-coupled device (CCD) camera system. The cell-gap map obtained is consistent with the shape of the reflector.

A novel fast‐switching LCD with dual‐domain bend mode

Abstract A novel fast‐switching LCD with dual‐domain bend (DDB) mode is described. DDB alignment is achieved using antiparallel‐rubbed cell filled with chiral‐doped LC. Initial alignment is mono‐domain 180‐degree twist. Tilt direction is controlled by oblique electric field to be counter direction in each domain. Twist‐to‐DDB deformation occurs continuously so that DDB mode does not require high‐voltage initialization which is inevitable in Optically Compen sated Bend (OCB) mode. DDB gives wide and symmetric viewing angle in contrast to mono‐domain bend formed from 180‐degree twist showing strong asymmetry.

P‐47: Evaluation Method of Gap and Pretilt Angle for Twisted‐Nematic Liquid‐Crystal Cells by Apparent Retardation Measurement using Two Wavelengths

We have proposed a novel method of evaluating a gap and a pretilt angle for TN cells from apparent retardation measured with different wavelengths. This method is suitable for the LCD estimation because of no voltage application and easy retardation measurement, even if the rough value of the gap is unknown.

P-48: Gap Distribution Measurement for Reflective Twisted-Nematic Liquid-Crystal Cells with Roughened Reflector

We have proposed a novel gap measurement method for reflective cells. This method evaluates the gap from the reflected light intensities considering the effect of the undesirable signal such as the surface reflection. The gap distribution over the roughened reflector can be obtained by this method.

Evaluation of reverse twist stability in an IPS mode

Abstract A reverse twist defect deteriorates a picture quality of an In-Plane Switching (IPS) mode display. We have proposed a simple method to evaluate the reverse twist stability using a sine curve director profile approximation. The calculated stability has been corresponded to the observed phenomena. Using this method, the stability dependence on the device parameters can be investigated with facility and the deterioration due to the reverse twist defect can be predicted. In the present study, the stability dependence on the rubbing angle, the driving voltage and the cell gap has been examined. The preferable cell gap condition has been suggested to prevent the reverse twist defect.