Dynamic response evaluation of liquid crystal with negative dielectric anisotropy

ABSTRACT

Rotational viscosity coefficient is an important material parameter affecting the dynamic response of liquid crystals. We evaluated the dynamic response of two series of mixed liquid crystals SCL17V33L00 and SCL17V28L00 with negative dielectric anisotropy on the basis of the accurate measurement of rotational viscosity. At the temperature of 25°C, 30°C and 35°C, the parallel and vertical dielectric constants of them were calculated from the dual-cell capacitance model and liquid crystal cell capacitance model. Then, the bend and splay elastic constants of them were determined by analysing the Fréedericksz transition threshold voltage in the vertically aligned nematic cell and comparing the liquid crystal layer capacitance–voltage curve through the finite-differential iteration method with experimental curve. At last, the rotational viscosity coefficients γ₁ of them were obtained by performing dynamic response simulation using Visual Fortran software. As the temperature increases, the rotational viscosity coefficient of them decreases. Although the rotational viscosity coefficient of the second mixed liquid crystal was relatively large under the same temperature, the viscoelastic ratio coefficient was small, and the figure-of-merit was large, thereby resulting in a relatively fast dynamic response.

Graphical Abstract

KEYWORDS:

• Rotational viscosity coefficient
• liquid crystal with negative dielectric anisotropy
• capacitance model
• dual-cell capacitance model
• dynamic response

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This research is supported by the National Natural Science Foundation of China (NSFC) [11374087, 11504080]; the Natural Science Foundation of Hebei Province of China [A2019202235, A2017202004]; the Key Subject Construction Project of Hebei Province University.