Ferroelectric liquid crystal materials applied to guest-host type displays

Abstract

Bistable ferroelectric liquid crystals (FLCs) suited for guest-host devices are described. Tilt angles of eight compounds and contrast ratios of the guest-host cells were measured as a function of temperature. The eight compounds were categorized into two classes. The first class exhibited the smectic A (S_A) phase with a tilt angle of around 22°. The second class did not show the S_A phase; the tilt angle was about 35° and almost constant over the temperature range of the smectic C(SC) phase. It was experimentally confirmed that the guest-host cell for the compound with the large tilt angle of 35° had a higher contrast ratio than 10. By using a binary system consisting of one compound from each class, influence of the tilt angle on bistability was examined. Increasing of the tilt angle improved not only the optical contrast ratio but also bistability.