Alignment control technology of liquid crystal molecules

• Published in: Journal of the Society for Information Display Vol. 28; no. 1; pp. 44 - 74
• Main Authors: Ishihara, Shoichi, Mizusaki, Masanobu
• Format: Journal Article
• Language: English
• Published: Campbell Wiley Subscription Services, Inc 01.01.2020
• Subjects: Alignment; alignment control; Anchoring; anchoring strength; Control methods; director direction; display mode; Flat panel displays; LCDs; Liquid crystal displays; order parameter; Order parameters; photoalignment; pretilt angle; rubbing; self‐alignment
• ISSN: 1071-0922; 1938-3657
• DOI: 10.1002/jsid.825

Liquid crystal displays are now indispensable in everyday life. The display characteristics considerably depend on the configuration of liquid crystal (LC) molecules and interactions between the LC molecules and an alignment film surface. In this paper, we introduce various methods to control parameters that dominate the LC alignment. These parameters include order parameters, the pretilt angle, the director direction, and surface anchoring strength. We also introduce their evaluation methods. In particular, recent alignment film‐free technology is explained in detail. In addition, details of how these parameters are related to the display characteristics, particularly wide viewing angles and fast response characteristics, are described primarily with reference to recent technologies. Most display characteristics of liquid crystal displays are determined by the alignment state of liquid crystals (LCs). In this paper, the control methods of the order parameter, pretilt angle, director direction, and surface anchoring strength, which determine LC configurations, are reviewed. Furthermore, the latest self‐alignment technology where alignment films are not required is explained in detail.