Control of liquid crystal pretilt angle by anchoring competition of the stacked alignment layers

Abstract

We proposed a method to control the pretilt angle of liquid crystals by stacking of a vertical alignment layer on a planar alignment layer. The pretilt angle can be controlled over the full range (0°–90°) depending on the thickness of the vertical alignment layer. We also proposed a numerical model to describe the physical mechanism based on the anchoring competition between liquid crystal, planar, and vertical polyimide alignment layers.

Alignment control technology of liquid crystal molecules

“… 4Fast response by alignment control: In multidomain VA (MVA) mode, it is known that rise time changes significantly from 8 ms to 209 ms depending on the geometry of sub‐domain arrangement pattern . Furthermore, an inorganic VA film of HfO 2 /Al 2 O 3 , and a laminated structure of a VA film and a planar alignment film with optimized anchoring energy exhibit fast response.…”

P‐139: Control of Liquid Crystal Pre‐tilt Angle Using Reactive Mesogen

“…However, the demand for intermediate pre-tilt angle has been gradually increased for new LCD modes and applications such as stable four domain twisted nematic (TN) mode [1] or fast response no-bias-bend mode [2,3]. Recently, various methods for controlling pre-tilt angle have been reported such as mixed alignment layers [4,5], stacked alignment layers [6], composite alignment layers using liquid crystal polymer (LCP) pillars [3]. These methods obviously show that the pre-tilt angle is controllable through an anchoring competition of planar and vertical alignment components.…”

Control of the molecular pretilt angle in liquid crystal devices by using a low-density localized polymer network

“…A similar approach was taken in [5]: the successful continuous adjustment of the pretilt angle in the range from 0°to 90°by tuning the surface hydrophobisity of the microgrooved silica substrates modified by organosilanes. Continuous control of a from 5°to 89°was achieved in [6] by depositing vertical-alignment PI layers of various thickness on a planar PI. Wide-range control of a was also achieved in [7] by using island metallic films, ion-beam treated a-C:F films [8] and SiC films [9] for LC alignment.…”