Reverse bistable effect in ferroelectric liquid crystal devices with ultra-fast switching at low driving voltage

Abstract

In this Letter, reverse bistable effect with deep-sub-millisecond switching time is first reported in ferroelectric liquid crystal (FLC) devices using a homogeneous photo-alignment technique. It is indicated by our experimental results that both the anchoring energy and the dielectric property of the FLC's alignment layer is critical for the existence of the reverse bistable effect. In addition, with the derived criteria of the reverse bistable effect, we quantitatively analyze the switching dynamics of the reverse bistable FLC and the transition condition between the traditional bistability and our presented reverse bistability. Moreover, the fabricated FLC device exhibits an ultra-fast switching of ∼160 μs and a high contrast ratio of 1000:1, both of which were measured at a low driving voltage of 11 V. The featured deep-sub-millisecond switching time is really advantageous for our presented reverse bistable FLC devices, which enables a significant quality improvement of the existing optical devices, as well as a wide range of new applications in photonics and display areas.

Ferroelectric Liquid Crystals: Physics and Applications

“…Ps > 50 nC/cm 2 ; Second, the two orientation states are separated by a relatively low energy boundaries, which is normally satisfied for anti-ferroelectrics [18][19][20]. For proper design the cell configuration and driving scheme, both Vshaped and S-shaped electro-optic response with multistability can be realized, as shown in Figure 9a,b [34,35]. The reverse bistable effect is observed in FLC devices [35], as shown in Figure 10.…”

“…Additionally, the clear distinction of traditional and reverse bistability facilitates the elimination of incomplete refreshing or negative images in bistable displays. It is validated experimentally that the depolarization field is responsible for the reverse bistability [35]. Considering the FLC cell with symmetric boundary condition, by applying the driving voltage of V0, the magnitude of the actual electric field applied on the FLC layer is:…”

“…To obtain the multistable electro-optical response, the following conditions should be satisfied: Firstly, sufficiently high spontaneous polarization FLC mixtures, e.g., Ps > 50 nC/cm 2 ; Second, the two orientation states are separated by a relatively low energy boundaries, which is normally satisfied for anti-ferroelectrics [18][19][20]. For proper design the cell configuration and driving scheme, both V-shaped and S-shaped electro-optic response with multistability can be realized, as shown in Figure 9a,b [34,35].…”

“…For proper design the cell configuration and driving scheme, both Vshaped and S-shaped electro-optic response with multistability can be realized, as shown in Figure 9a,b [34,35]. The reverse bistable effect is observed in FLC devices [35], as shown in Figure 10. Figure 10a,b shown the electro-optical responses of traditional bistable and reverse bistable effect.…”

“…The reverse bistable effect exhibits two stable states and is switched between two states by the falling edge of the driving pulses. The anchoring strength and dielectric property of the alignment layer is critical for the existence of the reverse bistable effect [35]. Potential applications of reverse bistable effect includes new design of energy-saving devices, such as e-paper, etc.…”