Switching hydrodynamics in multi-domain, twisted nematic, liquid-crystal devices

¹ The Rudolf Peierls Centre for Theoretical Physics 1 Keble Road, Oxford OX1 3NP, UK
² Mathematics Institute, University of Warwick - Coventry CV4 7AL, UK
³ INFM, Dipartimento di Fisica, Università di Padova Via Marzolo 8, 35131 Padova, Italy

Received: 21 February 2005
Accepted: 24 June 2005

Abstract

We study the switching dynamics in two-domain and four-domain twisted nematic liquid-crystal devices. The equilibrium configuration of these devices involves the coexistence of regions characterised by different handedness of the inherent director twist. At the boundaries between these regions there are typically disclinations lines. The dynamics of the disclination lines controls the properties, and in particular the switching speed, of the devices. We describe their motion using a numerical solution of the Beris-Edwards equations of liquid-crystal hydrodynamics. Hence we are able to explain why a conventional two-domain device switches off slowly and to propose a device design which circumvents this problem. We also explain the patterns of disclination creation and annihilation that lead to switching in the four-domain twisted nematic device.