Abstract
The ongoing interest in fast liquid crystal (LC) modes stimulated by display technology and new applications has motivated us to study in detail the in-plane switching (IPS) vertically aligned (VA) mode. We have studied how the decrease of the period of the interdigitated electrodes (down to sub-micrometer scale) influences the switching speed, especially the LC relaxation to the initial homeotropic state. We have found that there are two types of the relaxation: a fast relaxation caused by the surface LC sub-layer deformed in the vicinity of the electrodes and the slower relaxation of the bulk LC. The speed of the fast (surface) mode is defined by half of a period of the electrode grating, while the relaxation time of the bulk depends on the LC layer thickness and the length of the driving electric pulses. Thus, the use of the surface mode and the reduction of the electrode grating period can result in significant increase of switching speed compared to the traditional LC modes, where the bulk relaxation dominates in electrooptical response. We have studied thoroughly the conditions defining the surface mode applicability. The numerical simulations are in good agreement with experimental measurements.
Highlights
In 1997, Lee and co-workers discovered a new liquid crystal (LC) switching mode and called it vertically aligned in-plane switching (VAIPS) mode [1]
In the 2000s the agile display technology development trends turned to applications of the light-efficient fringe-field switching (FFS) mode developed by the same group of authors [5], and the VA-IPS mode was put aside
The electrodes were made either of transparent indium tin oxide (ITO) or opaque chromium coating prepared by vacuum sputtering
Summary
In 1997, Lee and co-workers discovered a new LC switching mode and called it vertically aligned in-plane switching (VAIPS) mode [1]. The experimental data and simulation results are especially important for understanding the influence of both the electrode grating geometry and the field-induced micro- and nanoscale LC deformation onto the switching dynamics. According to the simulated results for LC director distribution and local transmittance shown, the black stripes in the gaps between the electrodes (see Figure 5) correspond to walls with homeotropic LC alignment.
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