Al-doped zinc oxide (ZnO:Al) films were applied to liquid crystal displays (LCDs) as transparent electrodes substituting indium tin oxide (ITO). While the ZnO:Al-based twisted nematic LCD cell showed similar operational behavior to ITO-based counterpart, its electro-optical (EO) and residual dc (r-dc) characteristics were somewhat improved. Capacitance-voltage relations suggested that these improved EO and r-dc characteristics of the ZnO:Al-based LCD cell are due to the substantially lower density of charge carrier trapping centers in the polyimide layer∕electrode interface region, demonstrating high application potential of ZnO:Al films as transparent electrodes of LCDs.

We have investigated the generation of the pretilt angles for nematic liquid crystal (5CB) aligned in the cells using rubbed polyimide (PI) films containing trifluoromethyl moieties as a function of rubbing strength (RS). In order to characterize the films, we have conducted an analysis of the surface atomic concentration of fluorine (F) relative to that of carbon (C), F/C(%) with an electron spectroscopy for chemical analysis (ESCA) in the shallow surface region at the depth of 3 and 12 nm. It is shown that the F/C ratio at a depth of 3 nm decreases with RS, and that the observed pretilt angle shows a high value approaching 45° in the weak RS region, and tends to decrease with increasing RS. The existence of the trifluoromethyl moiety in the special PI, and its appearance in the surface region are considered to be responsible for the generation of high pretilt angles at low RS region since a surface covered by fluorine atoms has a low surface energy and the van der Waals dispersion force is thought to be dominant and hence perpendicular LC alignment is expected. With increasing RS the surface concentration of fluorine atoms decreases and repeated triangles will be formed; a combination of the dispersion force and steric interaction between LC molecules and these structures may cause a medium or low pretilted LC conformation.

We investigated the surface reformation of poly(dimethylsiloxane) (PDMS) elastomers by means of ion beam bombardment for fabricating wrinkle structures. Oxidation on the PDMS surface formed a silica-like outer layer that interacted with the inner PDMS layer, leading to the formation of wrinkle structures that minimized the combined bending energy of the outer layer and stretching energy of the inner layer. In addition, we controlled the amplitude and period of the wrinkle structures by adjusting the PDMS annealing temperature. As the PDMS annealing temperature was increased, the amplitude and period of the wrinkles formed by IB irradiation changed from 604.35 to 69.01 nm and from 3.07 to 0.80 μm, respectively.

We have studied the effect of the polymer tilt angle for pretilt angle generation in nematic liquid crystal, 4-cyano-4′-n-penthylbiphenyl (5CB) on rubbed polyimide surfaces. The polymer tilt angle was determined by measuring induced optical retardation produced in rubbed polyimide (PI) surfaces by rubbing. We suggest that the polymer tilt angle is not related directly to the pretilt angle on rubbed PI surfaces by rubbing. We proposed a microscopic model of pretilt angle generation on rubbed PI surfaces by rubbing. Finally, we conclude that the pretilt angle generation of 5CB strongly depends on the characterization of polymer materials and the micro-asymmetric triangular structure of the polymer on rubbed polyimide surfaces.

A characterization of rubbed polystyrene (PS) film in terms of the optical retardation measurement as a function of the rubbing strength (RS) has been made, and the alignment capability of the rubbed PS films for a nematic liquid crystal (5CB) has been investigated by measuring anchoring strength and its temperature dependence. It is shown that the liquid crystal (LC) molecules orient homogeneously in a direction orthogonal to that of rubbing, the anchoring strength of the rubbed PS films at the strongest rubbing strength for 5CB is about 70 times weaker compared to that for rubbed standard polyimide films, and the anchoring strength decreases with the temperature in a divergent fashion according to the increase of the extrapolation length toward the clearing point (T c=35.3°C).