Biphenyl derivative stabilizing blue phases

Abstract

After preparing a biphenyl derivative possessing two 2,3-difluoro-1,4-diphenylbenzene units, we investigated its phase transition behaviour. It showed a phase sequence of isotropic liquid–nematic phase–anticlinic smectic C phase. A mixture with a chiral additive with a high twisting power exhibited a cubic blue phase and/or an amorphous blue phase III (BPIII). The compound doped with 10 wt% of the chiral additive showed a phase sequence of Iso 85.4 °C BPIII 70.6 °C cubic BP 47.3 °C chiral nematic 37.3 °C unidentified smectic phase. We investigated electro-optical switching in BPIII and in the cubic BP of the mixture. Transmittance without an applied electric field in the BPIII was 0%, whereas that in the cubic BP was 4.6%. Threshold and driving voltages in the BPIII are lower than in the cubic BP. Furthermore, the BPIII exhibits no voltage-induced hysteresis effects on transmittance. Amorphous BPIII has superior potential for use in next-generation displays.