Optical measurement of flexoelectric polarisation change in liquid crystals doped with bent-core molecules using hybrid-aligned structure

ABSTRACT

We proposed an optical measurement method for determination of flexoelectric polarisation change in liquid crystals (LCs), which can be induced in highly distorted LC geometries. A hybrid-aligned nematic LC (NLC) mode was introduced to evaluate the direction and magnitude of the flexoelectric polarisation. We measured the DC offset amounts for equivalent brightness levels between forward and reverse bias vertical electric fields to estimate the sign and magnitude of e_s−e_b of flexoelectric coefficients. Additionally, the optical incident angle (α_max) for the maximum effective birefringence was investigated to predict the depth distribution of the LC director affecting the magnitude of the flexoelectric polarisation. The relationship between the variations of the DC offset and α_max by the flexoelectric polarisation changes was examined using the NLC mixtures doped with three selected bent-core LCs.

Graphical Abstract

KEYWORDS:

• Liquid crystal
• flexoelectric polarisation
• hybrid-aligned structure
• bent-core liquid crystal

Acknowledgements

This work was supported by the Technology Innovation Industrial Program funded by the Ministry of Trade, Industry & Energy (MI, Korea) [10052667, Development of high sensitive (< 30 mJ/cm2) R/G/B color photo-rewritable 3D holographic materials and 1 fps speed frame switching technology] and the LG Display Co., Ltd. For the elastic constant measurement equipment, we are grateful to Merck Ltd.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Technology Innovation Industrial Program funded by the Ministry of Trade, Industry & Energy (MI, Korea) [10052667, Development of high sensitive (< 30 mJ/cm2) R/G/B color photo-rewritable 3D holographic materials and 1 fps speed frame switching technology] and the LG Display Co., Ltd.