Akira Tagawa

Four states of surface-stabilized ferroelectric liquid crystal with parallel rubbing

The orientational states of surface-stabilized ferroelectric liquid crystals with parallel rubbing were investigated by changing the pretilt angle of the aligning film. Four states, C1-uniform (C1U), C1-twisted (C1T), C2-uniform (C2U), and C2-twisted (C2T) states, were observed. The C1U and C2U states showed extinction positions, whereas the C1T and C2T states did not. The memory angle of the C1U state was larger than that of the C2U state for the respective cells. The molecular orientational model of these states is discussed with regard to the experimental results.

Effect of surface pretilt angle on optical properties of surface-stabilized ferroelectric liquid crystals

Surface-stabilized ferroelectric liquid crystals (SSFLC) used with high-pretilt aligning film rubbed in a parallel direction showed three states, C1U, C1T and C2, which exhibited different optical properties. The temperature dependence of the memory angles of these states was measured for eight kinds of SSFLC sample cells which were prepared using two FLC materials and four aligning films. The increase in the surface pretilt angle made the memory angle of the C1U state greater, but did not affect that of the C2 state. The experimental results were quite consistent with the calculated relationships between the memory angle and the surface pretilt angle.

Electrooptic Effect in Homeotropically Aligned Ferroelectric Liquid Crystal

New types of electrooptic effects in a homeotropically aligned cell of ferroelectric liquid crystal have been proposed, and their characteristics have been studied. Especially, in the oblique incident type of the homeotropic cell, a new electrooptic effect with a sharp threshold, very fast response and a hysteresis loop is observed.

Electro-Optic Switching in Polymer Waveguide Using Surface Stabilized Ferroelectric Liquid Crystal

Abstract A fast electro-optic switching in polymer waveguide has been demonstrated using surface stabilized ferroelectric liquid crystal (SSFLC). In this device, the SSFLC layer is used as the active material with the passive polymer waveguide. The switching time is of the order of several microseconds.

Hybrid Optical Bistability Using Antiferroelectric Behavior in Ferroelectric Liquid Crystal

Hybrid optical bistability with an electrical feedback in surface stabilized ferroelectric liquid crystal which shows antiferroelectric behavior has been studied. The ac operation of the feedback without dc bias voltage is also realized in the liquid crystal which shows a symmetrical transmission-voltage curve. Dynamic characteristics of the switching between optical bistable states by an incident light pulse have also been studied.

Angular Dependence of Transient Light Scattering in Ferroelectric Liquid Crystal

Angular dependence of the transient light scattering in ferroelectric liquid crystal has been studied. The scattering during the polarity reversal of applied field can be divided into two parts. One is observed as a sharp peak of scattered intensity which has a fast response and may be correspond to the reorientation of the directors in bulk. The other is a broad peak whose response is relatively slow. This may originate from the nucleation and growth of reversed domain on the surface.

Driving Scheme for Ferroelectric Liquid Crystal Display with Multithreshold Method

Driving techniques for multithreshold method (MTM) ferroelectric liquid crystal displays (FLCDs) have been investigated. In MTM-FLCDs, each pixel is divided into two or more regions with different threshold voltages. Switching of each region is controlled by an adequate driving scheme and three or more gray scales should be achieved. However, when considering the pixel patterning effect, the width of 0% and 100% switching curves increases and a driving margin for the gray scale often disappears. We investigated some driving schemes by which to decrease the pixel patterning effect and found that a driving window for a gray scale could be achieved through the use of a preceding prepulse in a strobe voltage sequence.

Novel Switching with Gray Scale in Surface-Stabilized Ferroelectric Liquid Crystal Devices

The apparent tilt angle in surface-stabilized ferroelectric liquid crystals (SSFLCs) is dependent on the applied electric field for monostable and bistable devices. This behavior is attributed to the fact that the director profile of molecules in SSFLC cells is changed by an interaction between spontaneous polarization and the electric field. Based on this behavior, the transmission in SSFLCs can be controlled by the applied voltage, resulting in a smooth voltage-transmission curve.

Dynamic Characteristics of Optical Bistability and Limiting in Polymer Dispersed Liquid Crystal

Hybrid optical bistability and limiting using electro-optical effect in the polymer dispersed liquid crystal (PDLC) with electrical linear feedback have been studied. Optical limiting and bistability are realized for the case of negative and positive feedbacks, respectively. Dynamic properties of switching between optical bistable states by the incident light pulse are also studied. The switching can be realized by superimposing the light pulse of a very short duration (several hundred µs) on the incident light.

Dual Scanning Scheme for Ferroelectric Liquid Crystal Display

The dual scanning scheme (DSS) for ferroelectric liquid crystal displays (FLCDs) has been investigated. In DSS, two scanning electrodes are simultaneously selected and pixels on the two electrodes are switched to the black or white state in one unit time. We have investigated a DSS waveform set in which selected periods of two selected electrodes are duplicated. We found that the use of τ-Vmin mode FLC materials and the appropriate driving waveform set enables the simultaneous selection of two scanning electrodes and control of the FLC layers.