Liquid-Crystal Medium Composition for Fast Low-Voltage IPS Displays
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Solution Overview
Problem
Existing liquid-crystal compositions for FFS and IPS displays suffer from long addressing times, inadequate resistivity, high operating voltages, and inadequate low-temperature stability, which hinder their performance and shelf life.
Innovation Solution
A liquid-crystalline medium comprising compounds of formula I and Z, which provide positive dielectric anisotropy, high specific resistance, low threshold voltage, and improved low-temperature stability, enabling fast response times and reduced rotational viscosity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional liquid-crystal compositions are used in FFS and IPS displays, then the displays can operate, but they suffer from long addressing times and inadequate low-temperature stability
Solution Approach 1:
The patent modifies the chemical composition parameters of the liquid-crystal medium by incorporating specific compounds (cyclohexylbenzene derivatives with fluorine substitution, cyanobiphenyl compounds, and terphenyl compounds) in optimized ratios. This changes the physical parameters of the mixture to achieve both fast response times (γ1/K1 ≤ 4.0 mPa·s/pN) and improved low-temperature stability, resolving the contradiction between speed and reliability
Solution Approach 2:
The patent creates a composite liquid-crystal composition by combining multiple types of compounds (cyclohexylbenzene derivatives, cyanobiphenyls, terphenyls, and additives) with specifically optimized concentrations. This composite approach allows the mixture to exhibit both fast response characteristics and enhanced low-temperature performance that individual components cannot achieve alone
2Power
If existing liquid-crystal compositions are used, then displays can function, but they require excessively high operating voltages
Solution Approach 1:
The patent optimizes the dielectric anisotropy (Δε) parameter of the liquid-crystal composition by selecting compounds with appropriate polar groups (fluorine, cyanide) and aromatic structures. This parameter optimization reduces the threshold voltage to ≤ 2.5 V while maintaining composition stability and shelf life, resolving the contradiction between power consumption and reliability
3Loss of time
If conventional compositions are used, then displays can operate, but they have long addressing times due to high rotational viscosity
Solution Approach 1:
The patent directly targets the rotational viscosity (γ1) parameter by incorporating low-viscosity compounds and optimizing the molecular structure of the mixture components. The resulting composition achieves γ1/K1 ≤ 4.0 mPa·s/pN, which corresponds to fast response times ≤ 5 ms, resolving the time loss issue while maintaining manufacturability
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 medium achieves fast response times, high brightness, and improved contrast with reduced rotational viscosity, addressing the limitations of prior art compositions.
Implementation Method 1
Liquid-crystalline media having positive dielectric anisotropy... All these modes utilise an electric field which generated substantially perpendicular to the substrates and the liquid-crystal layer
Implementation Method 2
electrically controlled birefringence (ECB) modes... On application of a voltage to the electrodes an electric field with a significant component parallel to the LC layer is generated between them. This causes realignment of the LC molecules in the layer plane
Data Source
AI summary
The present invention relates to liquid-crystalline (LC) media having positive dielectric anisotropy and to liquid-crystal displays (LCDs) containing these media, especially to displays addressed by an active matrix and in particular to LC displays of the TN, PS-TN, STN, TN-TFT, OCB, IPS, PS-IPS, FFS, HB-FFS, XB-FFS, PS-FFS, SA-HB-FFS, SA-XB-FFS, polymer stabilised SA-HB-FFS, polymer stabilised SA-XB-FFS, positive VA or positive PS-VA type.