Takeshi Tani

Unidirectional layer alignment in ferroelectric liquid crystal with N*-C* phase sequence

Alignment of the smectic layer in ferroelectric liquid crystal which has a chiral nematic (N * )-chiral smectic C (SmC * ) phase sequence has been studied. The large-area monodomain has been realized by an ac field treatment. In this alignment, the layer normal is parallel to the rubbing axes even in a cell in which both the surfaces are rubbed

Dielectric Properties in Ferroelectric and Antiferroelectric Liquid Crystals with Isotropic-Chiral Smectic C Phase Sequence

Dielectric properties in ferroelectric and antiferroelectric liquid crystals which show isotropic (Iso.)→chiral smectic C (SmC*) and Iso.→chiral smectic CA (SmCA*) phase transitions have been studied. In the ferroelectric liquid crystal with the Iso.-SmC* phase sequence, two dielectric relaxations are observed under dc bias voltage. One appears around 700 kHz in frequency and is attributed to the soft mode. The other is related to the contribution of the Goldstone mode whose relaxation frequency is increased by the application of bias voltage. The antiferroelectric liquid crystal with the Iso.-SmCA* phase sequence also has two relaxations in the SmCA* phase. One originates from the molecular rotation around the short molecular axis and the other may correspond to the soft mode.

Physical properties of new phenylpyrimidine type ferroelectric liquid crystals

Abstract New phenylpyrimidine type ferroelecaic liquid crystals were synthesized and their mesomorphic and physical properties were studied. These compounds have chiral carbon directly linked to core part or methylene unit between chiral carbon and core aromatic ring. The internal methylene unit stabilizes liquid crystal phases thermally without increasing rotational viscosity. Sign of spontaneous polarization, twist sense of cholesteric phase and smectic C* phase do not exhibit odd- even effet concerned with internal methylene chain length.

Anomalous Behavior of Spontaneous Polarization in Ferroelectric Liquid Crystal Mixture

Anomalous behaviors of spontaneous polarization in a binary mixture of the chiral smectic and non-chiral smectic liquid crystals have been found. The spontaneous polarization P s of the ferroelectric liquid crystal possessing high P s decreases drastically upon doping with non-chiral smectic C liquid crystal. The sign inversion of P s is observed in a mixture highly doped with non-chiral liquid crystal.

Sign inversion of spontaneous polarization in ferroelectric liquid crystal mixtures

Sign inversion of spontaneous polarization (Ps) has been studied in two types of mixture systems of ferroelectric liquid crystal (FLC). One is a binary mixture of chiral (ferroelectric) and achiral SmC liquid crystals. Although the pure FLC has a relatively large Ps and shows no anomaly in the sign of Ps, the magnitude of Ps exponentially decreases upon doping with achiral compound. Particularly, in the mixture highly doped with achiral compound, which shows extremely small Ps, the sign of Ps is inverted upon changing temperature. In this case, the inversion temperature is very sensitive to the concentration of achiral dopant. Another system is a mixture of two FLCs having opposite signs of Ps. In this mixture, the sign inversion has been observed with temperature in the concentration range in which Ps is suppressed.

Alignment of surface-stabilized ferroelectric liquid crystal by the self-assembled monolayers of amphiphilic diacetylene derivatives

Surface-stabilized ferroelectric liquid crystal was aligned by the self-assembled monolayers (SAMs) of amphiphilic diacetylene derivatives formed on an indium tin oxide/glass substrate to maintain bistability when ferro-electric liquid crystal with high spontaneous polarization was used. The SAMs were disposed uniaxially either after rubbing them or passing them through a meniscus at a three-phase contact between a substrate, air, and n-hexane before exposing them to ultra-violet (UV) light. Infrared transmission spectra, contact angles against water and time of flight secondary ion mass spectra have revealed that the modified surface was a sparse monolayer of the diacetylenes, and that they were polymerized by UV light.

Physical properties of novel biphenyl and phenylpyrimidine type ferroelectric liquid crystals

Abstract A relationship between molecular structures and physical properties of novel biphenyl and phenylpyrimidine derivatives(1) is reported. These compounds have methylene chain directly linked to the core aromatic ring. The carbon number of alkyl chain has much influence on phase sequence, ferroelecmc properties and helical pitch in induced choles-teric phase. The phenylpyrimidine derivatives showed wider temperature range of Sc* phase compared with the biphenyl derivatives.

Syntheses and physical properties of new biphenyl and phenylpyrimidine type ferroelectric liquid crystals

Abstract New biphenyl and phenylpyrimidine type ferroelectric liquid crystals were synthesized and their physical properties studied. Each of these compounds has a chiral carbon atom directly linked to the core structure or has a methylene chain between the chiral carbon atom and the core moiety. The internal methylene chain and the core structure have an effect on the temperature range of the phase transition and the rotational viscosity in the Sc* phase, respectively.