Hiroshi Orihara

Ferroelectric Liquid Crystal Display Using Tristable Switching

Smectic layer structure and switching behavior in antiferroelectric liquid crystals TFMHPOBC, TFMHPDBC and MHPOBC were studied. At the phase transition point between SmC* and SmCA*, discontinuity in the leaning angle and the layer spacing was observed. In the SmA phase, diffraction peaks attributable to the focal conic texture and the planar layer structure were observed, implying that the bookshelf structure and the focal conic texture coexist. Using the tristable switching, we designed the fundamental waveforms for multiplex driving and constructed a prototype antiferroelectric liquid crystal display which works at room temperature.

A theory of D-E hysteresis loop

Abstract The D-E hysteresis loop of ferroelectrics is theoretically studied on the basis of the Avrami model, extended for the case of applied field dependent sidewise velocity. The exponent for the frequency dependence of the extended volume is obtained. The exponent of the area of hysteresis loop, with respect to the frequncy, is also obtained.

Simulations of Switching Behavior in a Ferroelectric Liquid Crystal

Simulations of the switching behavior in a ferroelectric liquid crystal were carried out with the model proposed by Handschy and Clark. There appear to be various types of switching processes for changing surface anchoring force. Results of simulations are compared with experimental observations, some of which seem to be well reproduced by the Handschy-Clark model.

Domain Observation in Pb(Zn1/3Nb2/3)O3–PbTiO3 Mixed Crystals

Domain-wall structures in the vicinity of the morphotropic phase boundary (MPB) in (1-x)Pb(Zn1/3Nb2/3)O3–xPbTiO3 (PZN–xPT) mixed crystals (x=5% and 8%) were investigated by means of a polarizing microscope. It was found that the apparent jump of the indicatrix rotation as a function of temperature appears in the MPB region (x=8%) without the poling process, indicating the occurrence of a phase transition between the tetragonal and rhombohedral phases, despite the fact that this transition is known to be observed only in a poled sample in the case of dielectric constant measurements. We concluded that the sharp phase transition between the tetragonal and rhombohedral phases in the PZN–PT crystal can be observed in the small region of 50 µm order even without the poling process. It was also found that the principal axis of the indicatrix slightly rotates in the MPB region, implying the appearance of the lower symmetry phase such as a monoclinic structure.

Theory of Morphotropic Phase Boundary in Solid Solution Systems of Perovskite-Type Oxide Ferroelectrics: Engineered Domain Configurations II

The piezoelectric constants under two types of engineered domain configurations in perovskite-type oxide ferroelectrics were calculated in terms of the Landau-Devonshire-type free-energy function. It was found that the piezoelectric constants under the engineered domain configurations increase on approaching the morphotropic phase boundary, and diverge at the morphotropic phase boundary, if the free-energy function is truncated at the fourth order in the polarization. The physical properties of the engineered domain configurations were discussed.

Ferroelectric Liquid Crystal Display with High Contrast Ratio

To obtain zig-zag defect-free liquid crystal cells by means of a standard rubbing technique, the effect of a new polyimide film on pretilt angle at a surface has been investigated. This new polyimide imposes the high pretilt over wide rubbing density, and good orientation of liquid crystals without zig-zag defects can be obtained for rubbing densities higher than 0.5×103. A new driving scheme to realize display devices with a high contrast ratio is proposed. This scheme is devised by utilizing anomalous switching behavior and AC-stabilized effect. The prototype of the ferroelectric liquid crystal display device shows the maximum contrast ratio of 40:1.

Brillouin and dielectric studies of the phase transition in the relaxor ferroelectric Pb(Ni1/3Nb2/3)O3

Brillouin scattering has been performed on the relaxor ferroelectric Pb(Ni1/3Nb2/3)O3 (PNN) from 80 to 450 K across its Curie temperature. A diffuse phase transition from the paraelectric to ferroelectric phase, associated with a broad phonon frequency dip and a damping maximum, is observed around 200 K. A relaxation mode in the form of a broad Rayleigh wing, whose frequency is strongly temperature dependent above 190 K, is observed and analyzed based on a modified superparaelectric model. Dielectric studies of PNN have also been carried out at several measurement frequencies. The relation between the measurement frequency and the dielectric maximum temperature was analyzed on a modified Vogel–Fulcher model.

Investigation of Switching Behavior in a Ferroelectric Liquid Crystal Aligned on Obliquely Deposited SiO Films

The effect of oblique evaporation of SiO on the chevron structure and the switching behavior in a ferroelectric liquid crystal have been investigated by means of the X-ray diffraction and the stroboscopic micrographs. It is found experimentally that the chevron direction and the domain structure appearing during the switching are determined by the direction of incidence of evaporated SiO. On the basis of the experimental results, it is clarified that the bow and the stern of the boat-shaped domain correspond to +2π and -2π internal disclinations, respectively. The structure of the zig-zag defect is determined.

Theory of nonlinear response

Abstract The dispersion formula of the third order susceptibility has been obtained on the basis of a free energy function, and it is compared with the experimental data obtained in a liquid crystal in its SmA phase. The higher order after-effect functions is discussed.

Switching Properties in Antiferroelectric Liquid Crystals

The influences of alignment materials on switching properties in antiferroelectric liquid crystals have been studied by using three kinds of polyimide resins. It has turned out that the threshold voltages of the switching between an antiferroelectric state and a ferroelectric state depend on the alignment materials, and that response times are also affected by the alignment materials.