Accurate determination on the pre-tilt angle of liquid crystal cell by combining optical and electrical measurement

ABSTRACT

In order to accurately determine the pre-tilt angle, we proposed a systematic method by combining optical and electrical measurement. First, the pre-tilt angles of the parallel and vertical aligned nematic liquid crystal (LC) cell with a large thickness (>10 μm) were measured by the crystal rotation method. Then, the material parameters of E7, including the dielectric constant and the splay and bend elastic constant, were obtained by using the dual-cell capacitance model and comparing the capacitance-voltage (C-U) curves of the thick cells. Finally, the pre-tilt angles of two thin LC cells to be tested were determined by theoretical and experimental fitting of their normalised C-U curve, which are 1.80°±0.04° and 3.50°±0.02°, respectively. Our method not only has relatively high accuracy, but also is not limited by the thickness and mode of LC cell.

KEYWORDS:

• Pre-tilt angle
• dual-cell capacitance model
• capacitance-voltage curve
• theoretical and experimental fitting

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by National Natural Science Foundation of China [11374087, 11504080]; Natural Science Foundation of Hebei Province [A2019202235 and A2017202004]; Research and practice project of Hebei Province higher education and teaching reform [2017GJJG018], Research Projects of Undergraduate Education and Teaching Reform in Hebei University of Technology [201802003], Project of College Students Innovation and Entrepreneurship Training Programme [201910080011] and Key Subject Construction Project of Hebei Province University.