Nematic Liquid Crystal Composition for Fast Response VA Displays
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Solution Overview
Problem
Liquid crystal compositions with negative dielectric anisotropy struggle to achieve simultaneously low viscosity, high elastic modulus, and refractive index anisotropy while preventing display failures such as ghosting and nonuniformity in high-speed liquid crystal display devices like televisions.
Innovation Solution
A liquid crystal composition combining specific compounds, including a compound with formula (I-1), formula (I-2), and compounds with negative dielectric anisotropy greater than 3, optimized in mass percentages to achieve low viscosity, low rotational viscosity, and high elastic modulus without reducing refractive index anisotropy or nematic phase-isotropic liquid phase transition temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If liquid crystal compounds with negative dielectric anisotropy are used to achieve high-speed response and wide viewing angles, then response speed is improved, but viscosity becomes too high preventing sufficiently fast response
Solution Approach 1:
The patent modifies molecular parameters by introducing specific fluorine atom substitutions at lateral positions (positions 2 and 6 of the phenylene ring) to change the physical properties of the liquid crystal compounds. This parameter change achieves negative dielectric anisotropy with larger absolute value while simultaneously reducing viscosity to enable high-speed response
Solution Approach 2:
The patent uses composite liquid crystal compositions containing multiple compounds including the specific compound of formula (I) with fluorine substitutions, compounds of formula (II), and compounds of formula (III). This composite approach combines the benefits of negative dielectric anisotropy with low viscosity characteristics to achieve both high-speed response and wide viewing angles
2Speed
If alkenyl compounds are added to improve response speed by reducing viscosity, then response speed is improved, but display failures such as ghosting and nonuniformity occur
Solution Approach 1:
The patent changes the chemical structure parameter by using fluorine-substituted phenylene compounds with specific molecular configurations that achieve low viscosity without the display failure problems associated with alkenyl compounds. The fluorine substitutions at lateral positions provide the necessary rheological properties while maintaining display reliability
Solution Approach 2:
The patent replaces the problematic alkenyl compounds with stable fluorine-substituted compounds that do not suffer from the same degradation and display failure issues, effectively substituting a reliable material for an unreliable one
3Manufacturing precision
If refractive index anisotropy is increased to improve display quality, then display quality is improved, but other properties such as viscosity and dielectric anisotropy become unbalanced
Solution Approach 1:
The patent simultaneously optimizes multiple parameters through the specific molecular structure of formula (I) with fluorine substitutions at positions 2 and 6. This structural parameter change achieves the desired refractive index anisotropy while maintaining appropriate viscosity and dielectric anisotropy values, balancing all critical properties
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The composition ensures high display quality and response speed with minimal display failures, suitable for active-matrix-drive VA mode and other display modes, by maintaining refractive index anisotropy and nematic phase-isotropic liquid phase transition temperature while achieving low viscosity and high elastic modulus.
Implementation Method 1
nematic liquid crystal composition with negative dielectric anisotropy (Δε) useful as a liquid crystal display material
Implementation Method 2
refractive index anisotropy (Δn) of the liquid crystal material must be adjusted within an appropriate range
Data Source
AI summary
The present invention relates to a nematic liquid crystal composition with negative dielectric anisotropy (Δε) useful as a liquid crystal display material, and to a liquid crystal display device using the composition. The liquid crystal composition of the present invention provides a liquid crystal composition that has sufficiently low viscosity (η), sufficiently low rotational viscosity (γ1), high elastic modulus (K33), and negative dielectric anisotropy (Δε) with a large absolute value without decreasing the refractive index anisotropy (Δn) and nematic phase-isotropic liquid phase transition temperature (Tni). A liquid crystal display device of VA-mode or the like that uses this composition is also provided, which has less or no display failures. The liquid crystal display device that uses the liquid crystal composition of the present invention is useful as an active-matrix-driving liquid crystal display device and can be used as a liquid crystal display device of VA-mode PSVA-mode, or the like.