Comparative Study of Director Responses in IPS and VA Modes Based Upon Physical Properties of Practical LC Materials

ABSTRACT

The director response times of pure IPS and VA modes were compared by inserting respective material constant values of practical LC mixtures into the equations based upon the Leslie-Ericksen theory. The VA mode was confirmed to be superior to the IPS mode from this aspect due to the difference of the Frank elastic constants for bend and twist. Further superiority was shown quantitatively because of the contribution of the back-flow effect in the VA mode. These results were supported by referring to the molecular theory of the physical properties of LC substances.

Keywords:

• Frank elastic constants
• nematic liquid crystal
• response time
• switching

Acknowledgments

The author wishes to express his appreciation to colleagues of LC R&D of Merck Ltd., Japan, and Merck KGaA, Germany, for the formulation of LC mixtures and the measurements of their physical properties. Special thanks are to Dr. Tarumi of Merck KGaA for many helpful discussions and Mr. Nakazono of Merck Ltd., Japan, for the numerical analysis of the accumulated data.