Yukihiro Kudoh

Application of an Electro Spray Deposition (ESD) Method to Control the Pre-Tilt Angle in a Nematic LC Cell

We applied the ESD technique to form an aligned LC layer with controlled pre-tilt angle. First, a horizontally aligned film was formed on the glass substrate by coating and rubbing. Then, a material promoting vertical alignment was sprayed using the ESD method. The aligned layer consisted of very fine domains mingled with horizontally and vertically aligned part. We were able to control the pre-tilt angle in a wide range by varying the amount of sprayed solution of the aligning material.

Control of Pre-tilt Angle and Evaluation of Azimuthal Anchoring Strength Considering the Pre-tilt Angle on the Alignment Film Formed by the ESD Method

The electrospray deposition (ESD) method is an established film-forming technique. The pre-tilt angle was controlled by using the improved ESD method has been proposed by our previous report. In this paper, a novel torque balance method for measuring an improved azimuthal anchoring strength for the high pre-tilt angle was proposed. The pre-tilt angle was controlled and the azimuthal anchoring energy depended on the pre-tilt angle was evaluated. The azimuthal anchoring energy was obtained in the range from 10−4 to 10−5 J/m2 depending on the pre-tilt angle.

Transient response characteristics of LCs with fiber grid structures assembled within the cell bulk

ABSTRACT The transient response characteristics of twisted nematic (TN) cells comprising a grid structure formed using polymer fibers within the cell bulk were investigated. The gap between the fibers of the grid was varied and the corresponding response time was observed. The decay response time was observed to reduce as the fiber gap became narrower. This suggests that the LC orientation force along the stretched direction of fibers becomes stronger as the gap becomes narrower. We have attempted to apply this grid structure to a memory-type liquid crystal display (LCD) as a three-dimensional LC orientation controlling technique.

A theoretical model of induced high pretilt angle by mixture of vertical and horizontal alignment materials

ABSTRACT Several methods for inducing high pre-tilt angles have been proposed. In our previous research, we proposed a time-division ESD method, which succeeded in controlling the pretilt angle over a wide range with tiny domains of alignment materials. In this study, we propose a model using a balance equation of the Rapini-Papoular theory for generating high pretilt angles on rubbed alignment films, which are formed according to our method. We compared theoretical values obtained using the model with reported experimental values and found that the results exhibit a good consistency.

DC switching of bistable textures in HAN cells with bistable surfaces fabricated using the oblique UV optical alignment technique

ABSTRACT Bistable surfaces for liquid crystal (LC) alignment were fabricated. A polyimide alignment film, which performed as a weak anchoring force film, was used, and the oblique-photo alignment method was used as an alignment process. Hybrid aligned nematic (HAN) cells with in-plane electrodes were assembled for inducing a flexoelectric polarization. The LC material was injected into the empty cells. When the polarization of the electric field was switched, the LC textures achieved polarity switching. In addition, the memory function of the LC texture was confirmed. Further, the application possibility for bistable liquid-crystal displays was shown using asymmetrically shaped electrode patterns.

A Novel Alignment Layer for Bistable Surface by Using Electrospun PVCi Microfibers

We propose a novel forming method for the bistable surface for the nematic LC with the poly (vinyl cinnamate) (PVCi) fibers, the fibers were spun by using the ES and were carried out the photo-alignment treatment by the UV irradiation. In this method, each stable state in the bistable states for the LC orientation might be realized. Because lots of fibers were stacked not only the substrate surface but also in the bulk of the LC cell, and then the anchoring force for the LC alignment was affected in three dimensions.

Measurement of Flexo-coefficients for Nematic LCs without the Influence of the Impurity Ions by Using the Chromatographic Isolation Method

The sum of the flexo-coefficients (e11+e33) was measured by the capacitance characteristic depending on the applied dc voltage in the HAN cell. The voltage for the minimum value of the capacitance was shifted by the influence of flexoelectric effect. One of the important problems for the evaluation for the flexo effect was the influence of impurity ions. Then, the chromatographic isolation phenomenon was used to separate impurity ions when the LC material was injected into the empty cell by the capillary action. The coefficient (e11+e33) of ZLI-4792 was measured, and a value of 26.0 pC/m was obtained.