Liquid Crystal Medium for Fast Switching and High Reliability
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Solution Overview
Problem
Current liquid crystal mixtures for electro-optical displays, particularly those based on the ECB, IPS, and FFS effects, face challenges such as high switching times, low contrast, and insufficient specific resistance, which affect their performance in extreme temperatures and long-term reliability, especially in applications like monitors and TVs.
Innovation Solution
The use of polar compounds with specific chemical formulas, such as those represented by formula I, which improve rotational viscosities and switching times, and are combined with other compounds to create mixtures with negative dielectric anisotropy, broad nematic phase ranges, and high elastic constants, enhancing the stability and performance of liquid crystal displays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional liquid crystal mixtures are used for ECB, IPS, and FFS displays, then the displays can operate with basic performance, but the switching times are high and contrast is low, affecting performance in extreme temperatures and long-term reliability
Solution Approach 1:
The patent applies parameter changes by modifying the chemical composition parameters of the liquid crystal mixture. Specifically, it incorporates compounds with specific molecular structures (cyclic carbonate groups, fluorinated chains) and controls the ratio of different components to achieve negative dielectric anisotropy values and optimized viscosity, thereby reducing switching times while maintaining reliability
Solution Approach 2:
The patent employs composite materials by creating a multi-component liquid crystal mixture that combines compounds with different functional properties. The mixture includes cyclic carbonate compounds, fluorinated compounds, and other liquid crystal materials in specific proportions to achieve synergistic effects that improve both switching speed and long-term stability
2Speed
If liquid crystal mixtures are designed for fast switching, then switching times improve, but specific resistance becomes insufficient and image sticking issues occur
Solution Approach 1:
The patent uses parameter changes by adjusting the dielectric anisotropy parameter to negative values through selective compound incorporation. This allows the mixture to achieve fast switching speeds while maintaining adequate specific resistance by balancing the polar and non-polar components in the mixture
3Ease of operation
If liquid crystal compounds with negative dielectric anisotropy are used, then switching performance improves, but the nematic phase range becomes limited
Solution Approach 1:
The patent applies composite materials by formulating a mixture that combines compounds with different phase behavior characteristics. The mixture includes fluorinated cyclic carbonate compounds that provide negative dielectric anisotropy alongside other liquid crystal materials that broaden the nematic phase temperature range, achieving both fast switching and wide operating temperature range
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
These mixtures exhibit improved switching times, high specific resistance, and low threshold voltages, ensuring reliable performance across a wide temperature range and reducing image sticking issues, thus addressing the limitations of existing liquid crystal technologies.
Implementation Method 1
electro-optical displays with active matrix addressing based on the ECB effect as well as for IPS (in-plane switching) or FFS (fringe field switching) displays
Implementation Method 2
The principle of electrically controlled birefringence, the ECB effect (electrically controlled birefringence)
Implementation Method 3
values for the dielectric anisotropy of Δε ≤ -0.5
Data Source
AI summary
The present invention relates to a liquid crystalline medium comprising at least one compound of formula I, wherein R1 and R1* each independently represent an alkyl or alkoxy residue with 1 to 15 C atoms, wherein one or more CH2 groups in these residues may also be independently replaced by -C=C-, -CF2O-, -OCF2-, -CH=CH-, -O-, -CO-O-, -O-CO- such that O atoms are not directly linked to one another, and wherein one or more H atoms may also be replaced by halogen, L1 and L2 each independently represent F, Cl, CF3 or CHF2, and its use for an active matrix display, in particular based on the VA, PSA, PA-VA, PS-VA, PALC, IPS, PS-IPS, FFS or PS-FFS effect.