Homogeneous and controlled surface induced alignment of rod-like molecules in the nematic liquid crystal (LC) phase is of central importance in today's flat panel displays. Most methods of surface preparation rely on anisotropic properties of relatively thin polymer layers, with which the boundary glass plates of the LC cells are coated. The anisotropy gives rise to surface easy axis orientation, along which the nearby LC molecules tend to align. The desired anchoring strength and spatial homogeneity of the surface is either obtained by mechanical rubbing, ultraviolet irradiation or strong external magnetic fields. Recently it was shown that also isotropic surfaces (i.e. surface layer formed from carbo-nanous material) can be used for alignment processes. The latter can be made anisotropic by ion beam irradiation, which is necessary for alignment purpose.

In spite of the exceptional development of various polymer alignment materials for LCD industry, the polymer alignment layers still represent the major source of the ionic contamination of the high resolution AM LCD. The increased ionic contamination in turn represents the major origin of the unwanted memory effects, which cause the degradation of the performance of the flat panel displays (reduced grey scale, switching speed,…).

We propose the new surface preparation method that relies on surface memory effect (SME). The proposed method does not require the presence of the polymer alignment layers, but is rather based on inorganic isotropic surfaces, which are relatively strongly responsive to the external fields. The signature for this property is a relatively high dielectric constant ε. According to the proposed alignment method the LC-cells are filled with LC in isotropic phase and finally cooled down into the nematic phase in the presence of a strong magnetic field B (B>2T) that is aligned along the symmetry breaking direction (e.g., along the x-axis) within the boundary glass plates of the LC-cell. The field orients the LC molecules along the x-axis. This orientation is imprinted on the surface and remains frozen-in due to SME. Our measurements indicate that the homogeneity and stability of the established homogeneous tangential anchoring condition along the x-axis improves significantly with increased ε. Various concepts for obtaining homeotropic anchoring will be discussed as well.

The main advantages of the proposed method are the following. i) With the present state-of-the-art superconducting magnets full size LCD cells can be aligned in reasonably short time (phase transition) and large volume – possibility for a mass production. ii) The established LC-substrate interface is free of any ionic contamination and strongly spatially homogeneous. iii) The anchoring conditions show long term stability at normal operating conditions. iv) π-twisted cells based on the proposed alignment method show significantly better characteristics in comparison with conventional π-cell design (smaller threshold voltage Vc; relatively gradual transmission decreasing on increasing V above Vc - adequate for grey scale purposes).

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†The research supported by the grant L1-6601-0106-04 of the ministry for Science of R Slovenia and grant # 444268-P050801 of Samsung, Korea