Naoko Mikami

New Ferroelectric Liquid Crystals with Spontaneous Polarization Exceeding 10−7C/cm2 and Their Electrical and Optical Properties

Abstract New series of ferroelectric liquid crystals with neighbouring chiral carbons or a chiral carbon with C—CI binding next to the molecular dipole moment (C=O) are synthesized utilizing isoleucine, valine, leucine, amylalchol and 2-amino butanoic acid as starting materials and are found to possess extremely large spontaneous polarization exceeding 3 × 10−7C/cm2 and dielectric constants larger than 7000. These compounds are found to exhibit a novel dielectric behaviour such as hysteresis in the temperature dependence due to the strong molecular interaction with surfaces. The response of electro-optic elements prepared with these ferroelectric liquid crystals is found to be very fast, in the μsec range, even at room temperature.

Characteristics of Optical Switching and Memory Effects Utilizing Deformation of Helicoidal Structure of Ferroelectric Liquid Crystals with Large Spontaneous Polarization

The anomalous voltage-transmission hysteresis of ferroelectric liquid crystals associated with the unwinding and winding of a helicoidal structure was studied in detail. Utilizing this phenomenon in newly developed ferroelectric liquid crystals with an extremely large spontaneous polarization, it is indicated that a bistable switching and memory element with a reasonable working voltage and response time can be realized.

Dielectric properties of new stable ferroelectric liquid crystals with large spontaneous polarization

New series of ferroelectric liquid crystals with two chiral carbons or bulky molecular components at the chiral carbon are synthesized and are found to possess extremely large spontaneous polarization exceeding 2×10−7 C/cm2 and a dielectric constant larger than 7000. These compounds are stable and exhibit a novel dielectric behavior due to the large spontaneous polarization and strong interaction with surfaces.

Anomalous Dielectric Behaviour in Biphenyl Ester Series of Ferroelectric Liquid Crystals

In ferroelectric liquid crystals of biphenyl ester series with alkylcarbonyloxy (CnH2n+1COO) chain length n longer than 9 exhibit anomalous dielectric behaviour. The spontaneous polarization becomes 0, even in the chiral smectic-C phase, at around 30°C at which the reversal of the sign of the tilt angle is observed, indicating a change of the sign of the spontaneous polarization. The origin of this anomalous behaviour is also discussed in terms of molecular interactions.

Synthesis and properties of ferroelectric liquid crystals with large spontaneous polarizations

Abstract The synthesis and some properties of optically active materials derived from amino acids will be described. Also we will report the properties of some compositions consisted of the chiral compounds and achiral Sc compounds. They have fast switching times at around room temperature.

Anomalous temperature dependence of the dielectric and optical properties in ferroelectric liquid crystals

Abstract The anomalous temperature dependence of the sign of the spontaneous polarization in a biphenyl ester series of ferroelectric liquid crystals is reported. The reversal of the sign of the spontaneous polarization in the chiral smectic C phase of 2MBNCBC ((S)-2′-methylbutyl-4′-n- nonylcarbonyloxy-(l,l′-biphenyl)-l-carboxylate) is observed at T m. This anomaly is studied in detail as functions of the length of the terminal alkyl chain, the applied electric field, the frequency and the applied hydrostatic pressure. T m has been confirmed to depend on the length of the terminal chain and the applied pressure. However, it is independent of the applied field and the measuring frequency. In the mixture of these compounds, this anomaly is also observed.

New series of ferroelectric liquid crystals with large spontaneous polarization and dielectric constant

Two new series of ferroelectric liquid crystals derived from haloalcohols as chiral sources are synthesized and are found to exhibit an extremely large spontaneous polarization of the order of 10−8–10−7 C/cm2 and also a large dielectric constant of 102–103 in a wide temperature range.

Bistability of Electro-Optic Effects in Ferroelectric Liquid Crystals

New type of bistable electro optic effects utilizing the transition between winding and unwinding states of helicoidal structure of the ferroelectric chiral smectic liquid crystals with large spontaneous polarization are studied. One effect uses the anomalous voltage-transmission hysteresis, and another effect uses the anomalous temperature-transmission hysteresis due to the balance between the forces of the chirality and the wall effect. In these effects the fast switching response is realized, and the special surface treatment and the optical polarizers are not required.

New Bistable Optical Switching Eletnent Utilizing Wound and Unwound States of Ferroelectric Liquid Crystal

A new type of bistable optical switching element utilizing differences of the scattering through the cell of ferroelectric liquid crystal in wound and unwound states has been established in 3M2CPOOB, in which both states can be stabilized due to the balance between the forces of the chirality and the wall effect.

Some Properties of Ferroelectric Liquid Crystals and Their Mixtures

Some ferroelectric properties, especially spontanious polarization directions and phase diagram of (R)-DOBA-1-MBC, (S) and (R)-DOBA-1-MPC and (S)-HDOBAMBC , have been examined. Relation between spontaneous polarization direction and molecular structure have been discussed.