Hiroshi Iwane

Thresholdless antiferroelectricity in liquid crystals and its application to displays

By diminishing the energy barrier between SCA* and SC*, antiferroelectricity has become thresholdless in a three-component mixture. It shows V-shaped switching, realizing attractive display characteristics: extremely wide viewing angle with very large contrast ratio, high speed response and ideal analogue grey scale with no hysteresis. A simplified model of the phase with this property is presented.

First Order Paraelectric-Antiferroelectric Phase Transition in a Chiral Smectic Liquid Crystal of a Fluorine Containing Phenyl Pyrimidine Derivative

The first-order phase transition between paraelectric SmA and antiferroelectric SmCA* phases has been observed for the first time in (S)-4-(1-trifluoromethylheptyloxycarbonyl)phenyl 4-(5-dodecyloxypyrimidin-2-yl)benzoate (TFMHPDOPB). Three pieces of evidence for the first-order phase transition are shown by means of DSC, X-ray and dielectric measurements. The DSC peak of the SmA-SmCA* transition is as large as the one for the Iso-SmA transition. The temperature dependences of the interlayer spacing determined by X-ray diffraction and of the dielectric constant reveal marked discontinuous jumps at the SmA-SmCA* phase transition.

On the appearance of the antiferroelectric phase

Abstract As the origin of the appearance of the antiferroelectric phase, the importance of dimerization of molecules in adjacent layers is pointed out on the bases of some experimental results. In thermotropic main chain polymer liquid crystals, the appearance of the antiferroelectric molecular orientation shows the odd-even effect concerning the number of spacer methylene unit. The same kind of odd-even effect was observed in low molecular weight liquid crystals, when the number of carbon atom, n, in chiral end is changed; the antiferroelectric phase tends to appear when n is even. The phase diagram in enamtiomeric mixtures of an antiferroelectric liquid crystal and the layer thicknesses in these mixtures also suggest the pairng of the molecules. The image of a scanning tunnelling microscope is also shown; the core parts of molecules align in a zigzag fashion.

Dielectric Studies on Antiferroelectric Liquid Crystals

Abstract The dielectric behavior in the first and the second order phase transitions between paraelectric SmA and antiferroelectric SmC*A has been explored using three substances having trifluoromethyl group. The soft mode contribution to the dielectric constants was easily obtained in both phases having no spontaneous polarization. The temperature dependences of the inverse dielectric strength 1/Δe, determined by the Cole-Cole plot clearly reveal the variety of the transition order such as the first-order and the second-order phase transition. The temperature dependences of the relaxation frequency also show the characteristics of these transition order.

Synthesis and thermal properties of antiferroelectric liquid crystals having phenylalkanoate and phenylalkenoate moieties

Abstract Novel antiferroelectric liquid crystals having phenylalkanoate and phenylalkenoate moieties were synthesized and their mesomorphic properties were studied. 4-[2-{1-(Trifluoromethyl)heptyloxycarbonyl}ethyl]phenyl 4′-decyloxybiphenyl-4-carboxylate 1b exhibited the chiral smectic CA phase at a temperature below the chiral smectic C phase. Biphenyl-cinnamate derivatives of the three-ring system exhibited a stable mesomorphic phase and enantiotropic smectic CA phase, with the carbon-carbon double bond acting as a mesogenic core.

Synthesis and physical properties of liquid crystal compounds having an alkoxyalkyl moiety at the asymmetric center

Abstract Novel antiferroelectric liquid crystal compounds, having an alkoxyalkyl moiety at the asymmetric center, were synthesized and their properties were studied.

Influence of the Optical Purity on the Smectic Layer Thickness and the Transition Order in Enantiomeric Mixtures of an Antiferroelectric Liquid Crystal

The transition behavior in the (R)- and (S)-mixtures of 4-(1-trifluoromethylheptyloxycarbonyl)phenyl 4-(5-dodecyl-oxypyrimidin-2-yl)benzoate (TFMHPDOPB) has been studied by X-ray diffraction. Two important findings were made. In all the mixtures, the transition is of the first order irrespective of the spontaneous polarization and the transition sequences; SmA-SmC*A (pure enantiomers), SmA-SmC* (R:S=3:1) and SmA-SmC (racemate). The layer thickness depends on the optical purity even in the SmA phase, although the overall profiles of the temperature dependence are almost the same in all the mixtures.