Electro-Optic Switching Behavior and Photorefractive Effect in Ferroelectric Liquid Crystals

**49**

**Chapter 4**

**Abstract**

*Akihiro Mochizuki*

have not been reported.

**1. Introduction**

In-Plane Retardation Switching

Smectic liquid crystals' layer structures and their influence on electro-optic characteristic properties are studied. Some background research works have revealed that a certain type of tilted smectic liquid crystal to the smectic layer normal showed some distorted out-of-plane retardation change. With intentional distortion of out-of-plane retardation change even provides almost in-plane only retardation change. In a certain type of smectic liquid crystal and its specific alignment condition, such a certain type of smectic liquid crystal panel shows in-plane only retardation switching. A more comprehensive study is still required, and such type of smectic liquid crystal panel provides unique electro-optic properties that

**Keywords:** smectic liquid crystal, smectic layer, tilted smectic, in-plane retardation,

Some smectic liquid crystals are known to show very different electro-optic effect compared to those of most of nematic liquid crystals. Although among nematic liquid crystals, some show unique electro-optic effect, most of nematic liquid crystals use their anisotropy of dielectric constant originated from dipole-momentum as their driving torque coupled with externally applied electric field. Under the restriction of orientational order on nematic liquid crystals, the dipole-momentum driving torque is fairly predictable. On the other hand, smectic liquid crystal molecules have some more restriction in their molecular switching than those of nematic liquid crystals due to their higher order molecule-molecule interactions than those for nematic liquid crystals. Such restriction may not be simply interpreted by higher viscosity as a bulk effect, but would be considered more intrinsic molecule-molecule interaction. Since the meaning of restriction does not mean slower optical response, but rather faster optical response than much less viscous nematic liquid crystal cases in a certain case of smectic liquid crystal electro-optic device. One of the purposes of this series of investigations is to understand how such restriction influences on retardation switching behavior such as in-plane and/or out-of-plane switching under the premise of in use for electro-optic devices such as display devices, phase modulation devices, beam steering devices and so on. In general, weaker molecule-molecule interaction gives more straightforward driving torque as the result of driving torque coupling from externally applied stimulation such as electric field application. Since

Behavior at Certain Types of

Smectic Liquid Crystals

out-of-plane retardation, chevron layer, bookshelf layer

## **Chapter 4**
