Shinichirou Oka

Electro-optical characteristics and switching behavior of a twisted nematic liquid crystal device based upon in-plane switching

A driving mechanism for a twisted nematic liquid crystal device that could possibly improve the viewing-angle characteristics and the cell gap error margin is proposed. It is important that the surface azimuthal anchoring strength of the liquid crystal cell differs at the upper and lower substrates, unlike a conventional twisted nematic (TN) mode. Electro-optical characteristics were investigated with an electric field applied in the plane of the substrates. It is numerically demonstrated and predicted that the proposed driving mechanism can have both the desirable features of in-plane switching mode (such as an excellent viewing angle) and those of a conventional TN type device (such as a small color shift and wide cell gap margin).

Determination of Polar Anchoring Strength at Vertical Alignment Nematic Liquid Crystal-Wall Interface Using Thin Hybrid Alignment Nematic Cell

A method of determining the polar anchoring strength Wd of a vertical alignment nematic liquid crystal-wall interface is proposed. Wd is evaluated from the measurements of the optical retardation of a thin hybrid alignment nematic cell as a function of the wavelength of the incident light and cell rotating angles. As an example, the anchoring strength Wd = 2.5 ×10-4 [J/m2] is measured at the interface between the nematic mixture ZLI-2293 and the polyimide vertical alignment film PI-1.

Optical Compensation Method for In-plane Switching Twisted Nematic Mode

We have proposed an in-plane switching twisted nematic (IT) mode. The characteristics of the IT mode are the wide viewing angle, the narrow cell gap error tolerance, and the relative fast response time. However, an IT mode needs a high electric field to obtain a high contrast ratio. To improve this situation, we propose a compensation method using a twisted nematic liquid crystal (LC) film or a twisted discotic LC film. Specifically, the latter can achieve the wide viewing angle, the high contrast ratio and the decrease in the driving voltage. In this paper, a compensation method using a film is suggested and evaluated by numerical calculation.

Electro-Optical Properties of the In-Plane Switching Twisted Nematic Mode

The important characteristics for display applications such as the response time, the color shift and viewing angle characteristics of the in-plane switching twisted nematic mode (IT mode) were investigated by means of experiments and numerical simulations. It was found that the fast response time of the IT mode approaches 10 ms, which is not inferior to that of a conventional twisted nematic mode. Based on the results, we emphasize that the IT mode can lead to the realization of excellent LCDs with a small color shift and wide viewing angle characteristics.

Relationship between Surface Order and Surface Azimuthal Anchoring Strength on Polyimide with Linearly Polarized Ultraviolet Light Exposure

The liquid crystal (LC) molecular order near the polyimide surface with linearly polarized ultraviolet (LPUV) light exposure is re-examined by the improved torque balance method. The surface azimuthal anchoring strength measured by the improved torque balance method is larger than that measured by the conventional torque balance method and is considered to be significantly affected by the phase transition behavior. On the basis of this result, it can be argued that the correlation between the LPUV light dosage and the surface azimuthal anchoring strength should be improved in considering of the surface order mechanism. The absolute surface azimuthal anchoring strength is investigated with respect to the phase transition characteristics. Photoalignment revealed that a relatively strong surface azimuthal anchoring strength may be obtained. Furthermore, the effects of photoalignment and rubbing of different alignment processes were examined.

Viewing Angle Characteristics and Cell Gap Tolerance of the In-plane Switching Twisted Nematic Mode

The electro optical (EO) characteristics of the in-plane switching twisted nematic mode (IT mode) were studied. The IT mode can have both the desirable features of the in-plane switching mode and the conventional twisted nematic mode. The excellent features such as the wide viewing angle characteristics and the preferable cell gap error tolerance were numerically and experimentally demonstrated. Even for the gray level transmittance, wide viewing angle characteristics can be confirmed.

Fabrication of Uniformly Vertical Alignment FLC Cell

We focus on vertical alignment ferroelectric liquid crystal (FLC) cells fabricated without the rubbing technique to realize FLC displays having high contrast ratio. In this study, we research the conditions for the fabrication of uniformly vertical alignment FLC cells in terms of the tilt angle of FLC and the anchoring strength of alignment film materials. As a result, the uniformly vertical alignment of FLC can be obtained in the case of the small tilt angle and the strong anchoring strength. Furthermore, we investigate the effect of the application of electric field on the vertical alignment.

Electro-Optical Characteristics of Twisted Nematic Liquid Crystal Device Based Upon in-Plane Switching

Previously, we reported unique features of a driving mode, named ‘In-plane switching Twisted nematic (IT) mode’. IT mode has excellent features of Twisted Nematic (TN) mode together with a merit of In-Plane Switching homogeneous mode. Remarkable features such as wide viewing angle and small color shift were confirmed by numerical simulation based on a continuum theory and 4 × 4 matrix method, and further the electro optical (EO) characteristics of IT mode LCD cell were numerically and experimentally shown.