Comparison of electro-optical switching between polymer-stabilised cubic and amorphous blue phases

Abstract

We prepared polymer-stabilised cubic and amorphous blue phase liquid crystals consisting of the same materials at different UV-curing temperatures using photopolymerisation. Then we investigated the effects of polymer stabilisation on their physical properties. The UV-curing temperature does not affect phase stabilisation of the polymer-stabilised amorphous BPIII (PS-BPIII). Temperatures of the PS-BPIII were found to be extended to more than 50 K. However, a critical temperature exists in the polymer stabilisation process for the PS-cubic BP. Although no substantial difference in response speed was found between the polymer-stabilised cubic and amorphous structures, larger hysteresis and higher residual birefringence were observed in the PS-cubic BP than in the PS-BPIII. Amorphous BPIII with an amorphous network of disclination lines has no critical temperature for the polymer stabilisation and realises a high-performance display.

Amorphous Blue Phase III: Structure, Materials, and Properties

“…Kikuchi et al performed polymer stabilization using a reactive mesogenic monomer [ 25 ]. Polymer stabilization has been applied not only to cubic BPI but also to amorphous BPIII [ 14 , 49 , 55 , 56 ]. Let us introduce our results here [ 14 ].…”

“…We compared the electro-optical properties in PS-BPIII with those in PS-cubic BP [ 55 ]. According to the design concept of a BP host LC, we prepared a host nematic mixture consisting of a rod-like nematic mixture ( 5CB (50 wt%), 8OCB (35 wt%), and 5CT (15 wt%)) and a BP stabilizer (10 wt%).…”

“… Optical texture of a sample in the PS-cubic BP at 25 °C without an electric field in the forward process ( a ), that with an electric field of 14 V·µm −1 ( b ), and that without an electric field in the backward process ( c ). The photographs are taken from [ 55 ]. Copyright (2015) Taylor & Francis.…”

Electro-optics of polymer-stabilised blue phase liquid crystal in in-plane switching mode

“…[12] These features of BPs lead to potentially interesting applications, such as mirrorfree lasers, tunable photonic crystals and fast switching displays. [13][14][15][16][17] However, narrow temperature range of their existence has limited such applicability. In 1993, Kitzerow et al stabilised the BP structure by polymerising the polymeric LC monomers, but BP cannot be switched because all the molecules were polymerised.…”

P‐148: Chiral Polymer Network of Polymer‐stabilized Blue Phase Liquid Crystals

“…In spite that the thermal stability has been much improved, there are still several problems which should be solved before the wide application of PS-BPLCs, including hysteresis, residual birefringence, and especially high driving voltage [6,7]. If the driving voltage of the PS-BPLCs is lowered, the lattice distortion caused by electrostriction will be reduced, and the hysteresis effect and the residual birefringence will be correspondingly improved [8][9][10][11]. Therefore, several methods have been proposed to improve the driving properties, such as the device structure optimization to increase the effective electric field [12][13][14][15] and materials development to increase the Kerr constant of BPLCs [16][17][18].…”