Liquid-Crystal Medium for IPS Displays with Low Voltage
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Solution Overview
Problem
Existing liquid-crystal displays face challenges with high operating voltage, long response times, and inadequate stability under extreme conditions such as UV exposure and heat, particularly in mobile applications, due to the limitations of dielectric anisotropy and viscosity of current liquid-crystal media.
Innovation Solution
A liquid-crystal medium comprising specific compounds with high dielectric constants and a high dielectric ratio, optimized for IPS and FFS displays, which includes a mixture of compounds from formulae B, I, II, III, IV, V, VI, VII, and IX, providing improved dielectric properties, reduced rotational viscosity, and enhanced stability across a broad temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If dielectrically negative liquid crystals are used to increase transmission, then transmission is improved, but operating voltage increases
Solution Approach 1:
The patent changes the dielectric anisotropy parameter from negative to positive values, and optimizes the ratio of perpendicular dielectric constant to dielectric anisotropy (ε⊥/Δε) to be 2.0 or less. This parameter transformation allows the liquid crystal to achieve high transmission while maintaining low operating voltage through the FFS effect mechanism.
Solution Approach 2:
The patent uses composite liquid crystal mixtures containing multiple compounds with different molecular structures (cyclic compounds, linear compounds, branched compounds) that collectively provide the desired dielectric properties. The composite formulation achieves both high transmission and low operating voltage by combining the effects of individual components with complementary properties.
2Ease of manufacture
If conventional liquid crystal compounds are used, then manufacturing is simple, but response time is long
Solution Approach 1:
The patent optimizes the rotational viscosity parameter by selecting compounds with specific molecular structures that reduce resistance to molecular reorientation. The positive dielectric anisotropy and optimized ε⊥/Δε ratio work together to accelerate response time while maintaining manufacturability through conventional liquid crystal formulation processes.
3Stress or pressure
If liquid crystal media with high dielectric constant are used to reduce threshold voltage, then threshold voltage decreases, but stability under extreme conditions deteriorates
Solution Approach 1:
The patent employs composite liquid crystal mixtures where different compounds compensate for each other's weaknesses. The mixture includes cyclic compounds for dielectric properties, linear compounds for thermal stability, and branched compounds for chemical resistance. This composite approach maintains high dielectric constant for low threshold voltage while achieving excellent stability under UV exposure, heat, and chemical conditions.
Solution Approach 2:
The patent incorporates compounds with inherent resistance to UV degradation, thermal decomposition, and chemical attack into the liquid crystal mixture formulation. These compounds provide beforehand protection against extreme conditions, ensuring long-term reliability while maintaining the required dielectric properties for low threshold voltage operation.
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 low threshold voltage, short response times, high transmission, and excellent stability under extreme conditions, enabling the development of liquid-crystal displays with improved energy efficiency and performance for various applications, including mobile devices.
Implementation Method 1
The liquid-crystal media according to the invention have a positive dielectric anisotropy and comprise compounds having at the same time large dielectric constants parallel and perpendicular to the molecular director
Implementation Method 2
IPS and FFS displays using dielectrically positive liquid crystals are well known in the field
Implementation Method 3
particularly the FFS (fringe field switching) effect using dielectrically positive liquid crystals
Implementation Method 4
The media are distinguished by a particularly high transmission
Data Source
AI summary
The invention relates to a liquid-crystalline medium having a nematic phase comprising one or more compounds of formula Bwherein the parameters have the meaning given in the text,to the use thereof in an electro-optical display, particularly in an active-matrix display based on the IPS or FFS effect, to displays of this type which contain a liquid-crystalline medium of this type and to the use of the compounds of formula B for improvement of the transmission and/or response times of a liquid-crystalline medium which comprises one or more additional mesogenic compounds.