Temperature influence on the dynamics of vertically aligned liquid crystal displays

Abstract

The strong influence of the complex reverse flow phenomenon on the dynamic temperature behavior of vertically aligned liquid crystal displays (VA-LCDs) has been demonstrated. Good agreement was obtained between theoretical and experimental switching profiles over a wide temperature range (25–75°C). This was achieved using the Leslie–Ericksen theory in a one-dimensional model with material viscosity coefficients obtained from an improved estimation procedure. Such accurate numerical simulations can have a large impact on further improvements of VA-LCDs (e.g., the development of temperature-compensating driving schemes).

Silicon oxides as alignment surfaces for vertically-aligned nematics in photonic devices

“…However, fall times were not affected. This effect remarkably alters the measurement of response times; it is attributed to the so−called backflow effect [15].…”

Effect of material properties on reverse flow in nematic liquid crystal devices with homeotropic alignment

“…This proves that the threshold V BF is a practical and relevant parameter to describe the viscous flow properties of liquid crystal materials for applications because the applicable voltage range in devices is limited by this threshold to achieve fast and reliable switching. 4 Knowledge of the Miesowicz coefficients becomes relevant when accurate modeling of the dynamic behavior is desired within the backflow regime ͑V Ͼ V BF ͒, but this is not required for most applications. Next to the dependence of V BF on the Miesowicz coefficients, as illustrated in Fig.…”

“…For instance, vertically aligned liquid crystal displays ͑VA-LCDs͒ have become very popular for mobile and television applications because of their excellent contrast ratio and wide viewing angle. However, their dynamic behavior 4 is affected by the possible occurrence of reverse flow, also referred to as backflow. When a voltage step with amplitude exceeding a certain threshold V BF is applied, the initial rapid variation causes reverse flow of the negative dielectric liquid crystal which leads to a complex reorientation mechanism ͑including a twist deformation͒ and a bounced transient transmission profile, 5 increasing the switching times.…”

Fast Switching of Vertically Aligned Liquid Crystals by Low-Temperature Curing of the Polymer Structure

“…Among the various LCD modes, the VA mode exhibits a superior dark state because the LC molecules are aligned perpendicular to the substrate in the initial dark state, resulting in a high contrast ratio [9,10]. However, the response time of the VA mode is not sufficiently fast to realize high-quality video [11,12]. To reduce the response time several methods have been proposed [13][14][15][16][17][18][19][20][21][22][23][24], but they have drawbacks, such as a complicated driving scheme, complex fabrication process, and increase in the operating voltage.…”