Liquid Crystal Medium Composition for Fast, Reliable VA and FFS Switching
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Solution Overview
Problem
Existing LC media with negative dielectric anisotropy in VA and FFS displays suffer from reduced reliability, high viscosity, slow switching times, and issues like image sticking and low VHR values, especially under UV exposure.
Innovation Solution
A liquid crystal medium comprising specific compounds of formulas I, III, IIIA, BC, and PH-1, which combine high birefringence with low rotational viscosity, enhancing solubility and stability, and reducing undesired mura effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If LC media with negative dielectric anisotropy are used in VA and FFS displays, then the displays achieve broad viewing angle and fast response times, but the reliability and VHR values are reduced
Solution Approach 1:
The patent modifies the chemical composition parameters of the LC medium by incorporating specific compounds (cyclohexane-1,3-dicarboxylate derivatives with fluorinated alkyl groups) to change the dielectric anisotropy and viscosity parameters, thereby improving both response time and VHR value simultaneously
Solution Approach 2:
The patent creates a composite LC medium formulation by combining multiple compounds including cyclohexane-1,3-dicarboxylate derivatives, terpenyl phenyl compounds, and fluorinated compounds in specific ratios to achieve synergistic effects that improve both speed and reliability
2Ease of manufacture
If existing LC media formulations are used, then the manufacturing process is simple, but the viscosity is high and switching times are slow
Solution Approach 1:
The patent changes the viscosity parameter of the LC medium by introducing compounds with specific molecular structures (low rotational viscosity compounds) while maintaining the overall formulation simplicity, achieving fast switching without complex manufacturing
3Ease of operation
If conventional LC media are used, then the display operates normally, but image sticking and mura effects occur under UV exposure
Solution Approach 1:
The patent uses stable LC compounds that resist UV degradation, replacing conventional LC materials that are susceptible to UV damage, thereby preventing image sticking and mura effects while maintaining normal display operation
Solution Approach 2:
The patent introduces UV-stable compounds that create a chemically inert environment within the LC medium, protecting against UV-induced degradation and preventing harmful effects like image sticking and mura
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 solution achieves fast switching times, high reliability, reduced image sticking, and improved VHR values, enabling energy-efficient displays with reduced driving voltage.
Implementation Method 1
the LC medium usually has a negative value of the dielectric anisotropy (As). In the switched-off state, the molecules of the LC layer are aligned perpendicular to the electrode surfaces (homeotropically) or have a tilted homeotropic alignment. On application of a voltage to the two electrodes, a realignment of the LC molecules parallel to the electrode surfaces takes place.
Implementation Method 2
These displays utilize an alignment layer prepared from crosslinkable and photoorientable monomers or prepolymers, e.g. cinnamate chromophores which are irradiated obliquely with linearly polarized UV light. As a result, a crosslinked alignment layer is formed which induces uniaxial alignment with a pretilt angle in the LC molecules close to its surface.
Implementation Method 3
A liquid crystal medium comprising specific compounds of formulas I, III, IIIA, BC, and PH-1, which combine high birefringence with low rotational viscosity
Data Source
AI summary
A liquid-crystal (LC) medium or LC material based on a mixture of polar compounds, its use for optical, electro-optical and electronic purposes, in particular in LC displays, especially in LC displays of the vertically aligned mode and/or the fringe-field switching mode, an LC display of the vertically aligned mode and/or the fringe-field switching mode comprising the LC medium, especially an energy-saving LC display, and a process of manufacturing the LC display.