Fast switching of long-pitch cholesteric liquid crystal device

Abstract

We propose a long-pitch cholesteric liquid crystal (ChLC) device capable of operation in both the dynamic mode and the memory mode. Fast switching between the homeotropic state and the focal conic state allows the display of moving pictures at a low operating voltage. In addition, we can write text messages on the proposed ChLC device by applying an external pressure locally to switch it from the focal conic state to the planar state.

Sub-millisecond nematic liquid crystal switches using patterned command layer

“…These range from changing the LC cell geometry and electrodes design, [2][3][4][5][6][7][8][9][10][11] to changing the LC structure from cholesteric to blue phase (BP). [12][13][14][15][16] Jo et al 8 combined two different LC cell architectures, the vertical alignment (VA) in the initial state and the four-domain twisted nematic (FDTN) with an external field stacking the VA layer onto the planar alignment layer, resulting in a rise time of 13 ms and a driving voltage of 6 V. TaeHoon Yoon et al 9 introduced a three-terminal electrode structure to simultaneously apply an in-plain and a vertical electric field, to show both bright state and grey levels, with the slowest grey-to-grey response of 9.6 ms and from grey to zero in less than 1 ms. Hun Ki Shin and collaborators 10 proposed a polarization switching device using an optically compensated pi cell for polarization-glass-type threedimensional display with a total dynamic response time of 2.5 ms. Won-Kyu Lee and collaborators 11 developed a new LC alignment layer combining single wall carbon nanotubes (SWNT) with a conjugate block copolymer and conventional rubbing, Yielding a high response time (3.8 ms), low operation voltages (1.3 V), and high thermal stability.…”

“…12,13 Recently a different class of LCs has emerged as a promising candidate for photonic and display applications, namely polymer-stabilized BP LC. 14 All these approaches show clear disadvantages.…”

“…14 All these approaches show clear disadvantages. In fact, to obtain sub-millisecond (ms) performances, high operating voltages (up to 100 V) are used, 12,13,16,17 while in the case of low operating voltages (below 50 V) typical switching times are longer than 10 ms or complex and elaborated architectures and materials need to be used. 9,10,18 Increasing attention has been devoted to micropatterned alignment surfaces, thanks to their flexibility in controlling the main LC alignment properties, such as pretilt angle and anchoring energy, compared to unidirectional alignment methods.…”

Dual mode operation of a chiral-nematic liquid crystal cell using three-terminal electrodes

“…Thus far, chiral nematic liquid crystal (CNLC) devices have been employed in various optical switching applications such as reflective display devices and light shutters, because of their bistable and reflective properties [1][2][3][4][5][6][7]. However, although switching from the planar to the homeotropic state occurs rapidly when a voltage is applied, relaxation from the homeotropic to the planar state takes approximately 300 ms after the applied voltage is removed, which is too slow for video application [3,7].…”

“…However, although switching from the planar to the homeotropic state occurs rapidly when a voltage is applied, relaxation from the homeotropic to the planar state takes approximately 300 ms after the applied voltage is removed, which is too slow for video application [3,7].…”