This paper proposes a vertical alignment cell based on a negative anisotropy nematic liquid crystal doped with pentacene. The device shows a lower operating voltage and faster dynamic response time compared to a vertical alignment cell without pentacene. The dielectric anisotropy, elastic constant and rotational viscosity of the pentacene-doped liquid crystal have been measured, and the results show that the low operating voltage and fast response time of the pentacene-doped vertical alignment cell is due to the increase of dielectric anisotropy and the decrease of rotational viscosity. Also, the frequency dependent dielectric relaxations of both the normal and the pentacene-doped nematic liquid crystal have been measured. As the result, it is shown that the pentacene lowers the dielectric response, which in turn reduces the rotational viscosity.

The pretilt angle of nematic liquid crystals on an alignment layer can be controlled from 2 to 89° by ion beam treatment of the alignment layer. Ion beam is used to partially destruct the vertical functional molecules of the vertical alignment materials. The ion beam-treated surface does not show any morphological difference from non-treated surface. The pretilt angles are generated by the remaining portion of the functional molecules in the material. The remaining portion of the molecules is dependent on the amount of ion beam exposure. We also apply this method to no-bend-bias-voltage optically compensated birefringence (OCB) mode with a pretilt angle of 55°. The OCB cell made by our method is a good candidate for high quality OCB mode because of the merits of uniformity of ion beam alignment and low power consumption of no-bend-bias-voltage.

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We report an anisotropy-enhanced polyimidization method in which the alignment surface coated with polyamic acid is ion beam-treated before polyimidization. The alignment substrate made by this method shows larger optical anisotropy than the rubbed and conventional ion beam-treated surfaces. Nematic liquid crystal (NLC) molecules are homogeneously aligned along the direction of the polyimidization. The LC cells fabricated by this method have lower pretilt angle and stronger anchoring energy than the cells fabricated by ion beam and rubbing method.

We investigated the horizontal alignment properties such as surface morphology, pretilt angle, and polar and azimuthal anchoring energy of organic alignment material-coated surface treated by ion beam. In this investigation the energy and incident angle of ion beam were changed. We also fabricated an in-plane switching (IPS) cell by ion beam alignment. The results showed similar voltage-transmittance characteristics to those of a rubbed cell and better dark state.