Effect of Non-DC Voltage Applied during N^*–SmC^* Phase Transition on Alignment of Half-V-Shaped Switching Ferroelectric Liquid Crystal

Abstract

In a half-V-shaped switching ferroelectric liquid crystal (half-V FLC), a liquid crystal material with N*–SmC* phase transition is used. When the material is cooled from N* phase to SmC* phase without an applied electric field, two types of domain with spontaneous polarization (Ps) in the upward or downward direction to the substrate plane are formed. In the conventional half-V FLC, a DC voltage is applied to the liquid crystal during the phase transition to form either type of domain selectively. Is the DC voltage application indispensable for selecting one domain? To clarify this point and to reduce the expected residual charge due to the application of the DC voltage, various waveforms of non-DC voltage were studied. We achieved the formation of one type of domain by applying an asymmetric rectangular waveform adjusted to cancel the effective DC component, and the generation of residual charge was avoided. The obtained half-V FLC alignment showed desirable black appearance in the crossed polarizers.

Improvement of alignment quality for FLC with mixing liquid crystal polymer

“…One typical FLC is commercial R2301 (Clariant, Japan), which has been reported by many researchers. FLC with I‐N*‐C* phase sequence is most attractive mainly because of its continuous gray levels and fast response, which are suitable for active devices such as thin film transistors (TFTs). However, one key obstacle for its practical application is to realize high quality alignment .…”

Free alignment defect, low driving voltage of half-V ferroelectric liquid crystal device

“…The horizontal chevron alignment defect is suggested to be suppressed when a dc electric field is applied during the N ‫ء‬ -SmC ‫ء‬ phase transition. 9,10 This dc voltage annealing process, however, is difficult to implement for the panel making due to the residual charges 11 and subpixels' electrode design. In this study, we approached the horizontal chevron alignment defect issue from the physical aspect of the FLC's elastic free energy.…”

Effect of Alignment Layers on the Response Time in a Half V-Shaped Ferroelectric Liquid Crystal Cell

“…Alignment of the uniform DS PI-A cell requires an external voltage during the phase transition to eliminate horizontal chevron defects. This might generate residual charges, 11) reducing the contrast of devices and generating defects in the thermal reestablishment process. Therefore, to maintain the characteristic of a faster rise time in the SS PI-A cell and to avoid the complicated method required for forming an HV-FLC mode in the DS PI-A cell, we used another cell structure: a DS PI-A/B cell.…”