Simple method for measuring the high pretilt angle of nematic liquid crystals

Abstract

Pretilt angle measurable by using the conventional crystal rotation method is limited to about 0°–20° and 70°–90°. We propose a method by which we can measure the pretilt angle by using the crystal rotation method even if the pretilt angle is between 20° and 70°. In this method, the determination of a pretilt angle is achieved by finding the rotation angles where transmittances are maximum and minimum in the periodic transmittance characteristics obtained with the variation of rotation angle.

Zenithal alignment of liquid crystal on homeotropic polyimide film irradiated by ion beam

“…The LC injection was carried out at room temperature. The pretilt angle was measured by the extended crystal rotation method which can measure a wider range of the pretilt [12,13]. …”

Pretilt angle of liquid crystal related to anisotropic polyimide layer thickness in a nematic liquid crystal cell

“…It is still a standard technique for aligning LC molecules in the LCD industry. The out‐of‐plane tilt angle as well as the in‐plane orientation of LCs are very important factors 6, 7. In optical configurations of LCDs, the pretilt angle is one of the most important parameters because it strongly influences the electro‐optical property of various LCD modes including twisted nematic mode,8 supertwisted nematic mode,9 ferroelectric LC mode,10 vertical aligned mode,11 and in‐plane switching mode 12.…”

Simultaneous Determination of Large Pretilt Angles and Cell Gap in Liquid Crystal Displays

“…Using the reference signals from the modulator controller, the first and second harmonics can be detected with a lock-in amplifier [8], [9]. Thus (8) (9) where is an instrument constant and is of no consequence.…”

“…Therefore, a simpler and more rapid technique is required. Several other techniques have been proposed [8], [9]. However, they all have difficulty measuring LCDs with a small cell gap ranging from 1 to 5 m.…”