Seo Hern Lee

A Multimode-Type Transflective Liquid Crystal Display Using the Hybrid-Aligned Nematic and Parallel-Rubbed Vertically Aligned Modes

We propose a transflective liquid crystal display (LCD) of the multimode type, which is composed of the hybrid-aligned nematic (HAN) mode in the reflective region and the parallel rubbed vertically aligned (PRVA) mode in the transmissive region. An optimized optical configuration is also proposed. In order to make the reflective and transmissive regions in one pixel independent, an Ar+ ion-beam alignment method was used. We confirmed that the transflective LCD of the proposed multimode type had high reflectance and transmittance, wide-viewing-angle property, and high contrast ratio.

Bistable chiral-splay nematic liquid crystal device using horizontal switching

The bistability in a chiral-splay nematic liquid crystal cell, which is obtained by adding a chiral additive to a splay cell, is proposed. In this letter, we describe a horizontal way of switching between the two states of the bistable chiral-splay cell, one state being characterized by a nontwisted director field with splay, the second state showing a director-field with 180° twist. The optimization of the various parameters of the device is described.

A Novel Transflective Liquid Crystal Display with a Periodically Patterned Electrode

We propose a novel transflective liquid crystal display (LCD) with a periodically patterned electrode on a substrate. By optimizing the pattern size of the electrodes, the retardations which are required in reflective and transmissive modes are periodically achieved by the same voltage. The region with a small retardation is used as reflective mode and the region with a large retardation as transmissive mode. In the proposed transflective LCD, we can expect a very simple manufacturing process and a high optical performance as complex process such as a multi-cell gap process and multi driving method are not applied.

Simple method for measuring the high pretilt angle of nematic liquid crystals

Pretilt angle measurable by using the conventional crystal rotation method is limited to about 0°–20° and 70°–90°. We propose a method by which we can measure the pretilt angle by using the crystal rotation method even if the pretilt angle is between 20° and 70°. In this method, the determination of a pretilt angle is achieved by finding the rotation angles where transmittances are maximum and minimum in the periodic transmittance characteristics obtained with the variation of rotation angle.

Low-Cell-Gap Measurement by Rotation of a Wave Retarder

A simple method of measuring the cell gap of a low-cell-gap twisted nematic liquid crystal (TNLC) cell is proposed. Unlike the conventional methods which make use of a rotatable polarizer and analyzer or a compensator set between a pair of crossed polarizers, the proposed method uses a wave plate set on top of a motor by which we rotate the plate by 360°. With the proposed method, we can measure the cell gap of TNLC cells with a low cell gap below 4 µm. The proposed method can also be applied to single-polarizer reflective LC cells.

Transflective liquid-crystal display using low-twisted vertically aligned mode

We present the design of a transflective and low-power LCD using a low-twist vertically aligned liquid crystal (LC) cell, achieved by blending a chiral additive with a patterned reflector in a single-domain configuration. Unlike the conventional single-domain transflective LCD, in which it is possible to optimize only one of the transmissive and reflective regions, the device suggests that it is possible to optimize both the transmission and reflection design to obtain favorable results in both reflective and transmissive light conditions by optimizing the chiral pitch and twist angle. From the parameter space diagram (PSD) method, which does not include the information on chiral pitch and the nonuniform LC director tilt angle, optimization focused on the transmissive region is performed. By analyzing the relation between the transmittance and the chiral pitch under the applied voltage, the optimized twist angle and chiral pitch are proposed. It is described that the optimized twist angle is also available for the reflective region by the dynamic PSD method by considering the average tilt angle under applied voltage.

Geometric Structure for the Uniform Splay-to-Bend Transition in a π-Cell

A novel geometric structure for achieving a uniform splay-to-bend transition in a π cell is proposed. In order to obtain the uniform bend transition, we formed a hybrid domain structure at the edge of a liquid crystal cell by the ion-beam alignment method. We found that the uniform bend transition spreads from the edge of a π cell to the bulk region. With the proposed structure we can achieve a reliable and uniform bend transition in a π cell.

Novel cell gap measurement method for a liquid crystal cell

We propose a novel method of determining thickness of a liquid crystal cell by measuring the total intensity ratio (TIRM) of the transmitted light at two arbitrary wavelength regions. The proposed method can be applied to the measurement of small cell gap as well.

Optimized configuration for transmissive and reflective bistable chiral-splay nematic liquid crystal device

The optimized configurations to use a bistable chiral-splay nematic liquid crystal cell as transmissive and reflective display are calculated using the Mueller matrix method. By numerical calculation, nontwist 0° splay state of bistable states is optimized so that the dark state is completely achieved over the entire visible-wavelength range. Based on the optimized conditions, we have experimentally demonstrated a high-contrast ratio of 200:1 in transmissive display and 40:1 in reflective display without using a wideband retardation film.

A New Design of Optical Configuration of Transflective Liquid Crystal Displays using Antiferroelectric Liquid Crystals and Frustelectric Ferroelectric Liquid Crystals

We propose an optical configuration of transflective antiferroelectric liquid crystal (AFLC) and frustelectric ferroelectric liquid crystal (FR-FLC) display modes using a half-wave LC cell in which the in-plane tilt angle is 22.5°. It is composed of two polarizers, an AFLC or FR-FLC cell, two achromatic quarter-wave films, and a transflective film layer. In the case of using it in the reflective mode, it provides a high brightness and a high contrast ratio, and in the case of using it in the transmissive mode, it also provides a high contrast ratio. By fabricating modes of a transflective liquid crystal display (LCD) with a half-wave retardation, we demonstrated high brightness as well as high contrast ratio of a half-wave by the commercial simulator (DIMOS).