Tomio Wada

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.

Models of Molecular Orientation in Surface-Stabilized Ferroelectric Liquid Crystals with High-Pretilt Aligning Film

Surface-stabilized ferroelectric liquid crystals (SSFLC) with high-pretilt (about 15°) aligning film showed three types of states (C1U, C1T and C2) with different optical properties. The transmitted light of these states was calculated using the 4×4 matrix method, and the optical memory angle and transmission spectra were compared with the experimental observations. The experimental characteristics of these states were consistent with the calculated results, indicating the validity of the proposed molecular orientational models of these states. In addition, we simulated the effect of the pretilt angle of the aligning film on the optical properties of the SSFLC device.

The states of surface-stabilized ferroelectric liquid crystal with high-pretilt aligning film

Surface-stabilized ferroelectric liquid crystal with high-pretilt (about 15°) aligning film rubbed in parallel showed three types of states: C1-uniform (C1U), C1-twisted (C1T), and C2 states. In the C1 state, the uniform state (C1U) showing extinction positions and the twisted state (C1T) showing no extinction position were observed. On the other hand, the C2 state showed only one state showing extinction positions. The properties of these three states were investigated and their orientational model will be discussed in combination with the molecular orientation on the surface of the aligning film.

Study of molecular orientational states of ferroelectric liquid crystals in a surface stabilized geometry

Abstract The molecular orientational states of homogeneously aligned, helix unwinding, chiral smectic C liquid crystals placed in a thin cell (surface-stabilized ferroelectric liquid crystals [SSFLC]) were studied. They were classified by the optical viewing conditions and the relationship between the directions of the chevron layer structure and the surface pretilt. The molecular orientational models of the states were considered and illustrated with regard to the experimental results. The models of molecular orientation give us a total understanding of the orientational states which appear in SSFLCs with parallel rubbing. Furthermore, the effect of the surface pretilt angle on the orientational and optical properties of SSFLCs is discussed.

Ferroelectric liquid crystal device using the τ-VMIN mode

Abstract Ferroelectric liquid crystal (FLC) devices using the -Vmin mode were developed, combining FLC materials with negative dielectric anisotropy, the C2-uniform (C2U) orientational state and the “Malvern” drive schemes. The developed FLC materials in these devices showed the Vmin value under 35V, which is adequate to the drive voltage of ±40V. The C2U orientational state was found to be the preferred state for the -Vmin mode, and was obtained in FLC cells with medium pretilt aligning film. The FLC cells were driven by the Malvern drive schemes, achieving fast line address time (faster than 50μ sec/line), wide temperature range of driving (0∼40°C), high contrast (higher than 50:1) and drive voltage of ±40V.

Ferroelectric Liquid Crystal Mixtures Containing Chiral Pyranose Compounds for Response-Voltage Minimum Mode

Ferroelectric liquid crystal (FLC) materials for the response-voltage minimum (τ–Vmin ) mode were developed by doping novel chiral pyranose compounds into achiral host materials with negative dielectric anisotropy. The chiral pyranose derivatives, wherein three chiral centers and a trifluoromethyl group were fixed in the 6-membered ring, induced short τmin in the τ–Vmin characteristic. The developed FLC materials were driven by drive schemes for the τ–Vmin mode, giving short line address times.

Layer Tilt Angle of Chevron Structure in Surface-Stabilized Ferroelectric Liquid Crystals

Smectic layer structures of some surface-stabilized ferroelectric liquid crystal cells were studied using high-resolution X-ray analysis. The cells were constructed of two glass plates coated with a polymer aligning film rubbed in parallel and exhibited a typical chevron layer structure. The correlation between the layer tilt angle and the molecular tilt angle was investigated in detail, taking into account the differences between the molecular tilt and apparent tilt angles. It was confirmed that the layer tilt angle correlated with the molecular tilt angle though it was slightly smaller, and the ratio of the layer tilt angle to the molecular tilt angle gradually decreased as the molecular tilt angle increased.

Influence of Deformation of Smectic Layer Structure on Dielectric Behavior of Ferroelectric Liquid Crystal.

The dielectric permittivity of a surface stabilized ferroelectric liquid crystal (SSFLC) cell was found to be influenced by the electric field treatment, which changed the smectic layer structure and the cell texture. The relationship between the dielectric permittivity and the texture change was studied, considering the effect of the deformation of the smectic layer structure on the dielectric behavior of SSFLC.

Measurement method of dielectric permittivities of ferroelectric liquid crystal based on molecular orientational models

Abstract The measurement method of the dielectric permittivities of FLC based on the molecular orientational models (MOM method) is presented. The dielectric permittivities are measured by using usual SSFLC cell directly, not from the helical structure or the achiral host material. The measurement results are reported and the propriety of MOM method is discussed.