Novel properties of high-performance multi-component mixture for Vertically Aligned mode LCDs

ABSTRACT

Vertically Aligned mode Liquid Crystal Displays (VALCDs) which have generated huge research interest due to their excellent contrast and wide viewing angle require materials with negative dielectric anisotropy. This work highlights the systematic development of a fifteen-component mixture from pure liquid crystalline compounds comprising laterally fluorinated bi-, tri- phenyl, tolane, bicyclohexane compounds and non-mesogenic compounds exhibiting negative dielectric anisotropy. The temperature dependence of birefringence (Δn), dielectric anisotropy (Δε), threshold voltage (V_th), bend elastic constant (K₃₃), relaxation time (τ₀) and rotational viscosity (γ₁) as a function of temperature of this fifteen-component nematic mixture have been reported. This mixture exhibits a high Figure of Merit (FoM) which is desirable for reducing the device response time. Additionally, the orientational order parameter (OOP) values, activation energy (E_a), visco-elastic co-efficient (γ₁/K₃₃) and material parameters (A₀) have also been reported. The effect of pretilt angle in the alignment layers on the threshold voltage (V_th) and switching time (τ₀) to ascertain the applicability of this material in Vertically Aligned mode Liquid Crystal Displays (VALCDs) have also been discussed.

GRAPHICAL ABSTRACT

KEYWORDS:

• VA-LCDs
• multi-component mixture
• negative dielectric anisotropy
• birefringence
• bend elastic constant
• pretilt

Acknowledgments

Financial support from DST, New Delhi (Project No: Sr/S2/CMP-29/2007) to B Das is gratefully acknowledged. One of the authors

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The work was supported by the Department of Science and Technology, Ministry of Science and Technology, India [Project No: Sr/S2/CMP-29/2007].