Orthoconic antiferroelectric liquid crystals for multimedia LCD's

Abstract

Ferroelectric smectic liquid crystals (FLC) were considered for high speed, high contrast displays and other high speed devices without the need of transistors and other active elements i.e., in passive matrix structures. However due to such obstacles like poor mechanical durability of the structure and tremendous scientific difficulties of a very basic nature their wide application is still hindered. Close related and similar polar smectic antiferroelectric liquid crystals (AFLC) offer less complicated solutions for high demanding applications and like FLC's, they are capable of fast, in-plane switching. Among all known AFLC's those exhibiting extremely high molecular tilt, reaching 45°, called orthoconic AFLC's (OAFLC's) seems to be most promising for display application.OAFLC's are unique materials which in the surface stabilized structure (SSOAFLCs) show a peculiar electrooptical behavior. SSOAFLCs become an optically uniaxial and optically negative medium, with the optical axis perpendicular to the substrates plane. Due to this property SSOAFLCs provide excellent dark state at the normal incidence, hence an extremely high contrast, regardless of the surface stabilized structure defects. Such SSOAFLC's exhibiting threestable switching provide inherent gray scale capability, video-rate performance speed simultaneously with hemispheric viewing angle and remarkable mechanic durability. Due to this SSOAFLC are candidate for future passive multiplexed driving working displays with symmetric driving schemes and easy of gray scale generation.A key physical properties of OAFLC's are presented as well as their significance for the display manufacturing is discussed.