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In this paper, the liquid crystal (LC) order parameters of the interface layers at rubbed polymer surfaces were studied. The LC films in this study were made with either polyvinyl alcohol or polyimide and the test LCs were filled into wedge-shaped cells for various measurements. The real distribution of order parameters from LC bulk to the interface was obtained by measuring the anisotropic infrared absorbance of sample films. It was found that the order parameters start to decrease where the LC layer thickness is smaller than 10 nm, and the order parameter of LC monolayer at the rubbed polymer surface is only 1/3–1/2 of that of the LC bulk even in a strong rubbing condition. When the temperature was increased to the transition point, the LC interface layer (excluding the adsorption monolayer) completed the phase transition while the bulk layer remained in LC phase. This was a further evidence that the order parameter of the interface layer is lower than that of the bulk. [ABSTRACT FROM AUTHOR]

Even a quite small amount of ions added to liquid crystals (LCs) adsorbs to the surfaces of the alignment films in liquid crystal cells. For the investigation of such adsorption, two liquid crystal cells were prepared. We used a polyimide having benzene moieties as the alignment film material. One cell was filled with a liquid crystal including a cyano group and the other with a fluorinated compound. For both cells, the activation energy (determined by measurements of residual direct current voltage at various temperatures) of the adsorption for the ions to the surfaces of polyimide films were below 0.3 eV. The results indicate that the adsorption takes place due to van der Waals interaction, hydrogen bonding, or ion-πr interaction between the ions in the LCs and the polyimide films. [ABSTRACT FROM AUTHOR]

Optically compensated bend mode (OCB-mode) [1,2] LCD is promising for next generation displays, because it offers the fast response times and a wide viewing angle. However, this mode requires a transition of the liquid crystals from an initial splay state to bend state before operation. This study analyzed the conditions under which this transition is generated. Consequently, a method of creating a transition nucleus for splay to bend state by controlling the boundary of right and left twist state and that of asymmetrical up and down state was established. [ABSTRACT FROM AUTHOR]

Investigates the critical splay-to-bend-alignment transition in a liquid-crystal cell treated by parallel rubbing. Purpose of proposing an optically compensated bend mode; Analysis of free energy in liquid crystal cells; Reduction of the required optical anisotropy of the liquid-crystal cell.