Liquid Crystalline Medium for Fast Switching Displays
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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 limited viewing angle dependence, along with issues of image sticking and stability over long operational periods, especially at extreme temperatures.
Innovation Solution
The use of specific liquid-crystalline media containing compounds of a particular formula, which exhibit negative dielectric anisotropy, low rotational viscosities, and high elastic constants, enabling improved switching times, stability, and reduced image sticking across a wide temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If conventional liquid crystal mixtures are used for ECB, IPS, and FFS displays, then the displays can be manufactured with standard materials, but the switching times are high and image sticking occurs over long operational periods
Solution Approach 1:
The patent changes the chemical composition parameters of the liquid crystal mixture by introducing specific compounds with fluorinated groups and cyanobiphenyl structures. These compositional changes result in optimized physical parameters including reduced rotational viscosity (γ1 ≤ 165 mPa s at 20°C) and adjusted dielectric anisotropy (Δε ≤ -0.5), which directly improve switching times while maintaining stability and preventing image sticking during operation
Solution Approach 2:
The patent creates a composite liquid crystal mixture containing multiple specific compounds including cyanobiphenyl derivatives, fluorinated compounds, and other nematic liquid crystal materials in defined proportions. This composite formulation combines the advantages of different molecular structures to achieve both fast switching characteristics and long-term operational stability, resolving the contradiction between speed and reliability
2Speed
If liquid crystal mixtures with fast switching times are developed, then switching performance improves, but stability and resistance to image sticking over long periods deteriorate
Solution Approach 1:
The patent optimizes physical parameters by selecting compounds with specific molecular weights, aspect ratios, and intermolecular interaction strengths. The resulting mixture achieves a balanced parameter set where rotational viscosity is sufficiently low for fast switching while elastic constants and dielectric properties maintain stability, preventing image sticking during extended operation
Solution Approach 2:
The patent introduces compounds with localized fluorinated groups and specific functional moieties that provide distinct local properties within the liquid crystal mixture. These localized structural features contribute to both fast switching in the nematic phase and enhanced stability during operation, allowing simultaneous optimization of speed and reliability
3Power
If liquid crystal compounds with high dielectric anisotropy are used, then switching response improves, but rotational viscosity increases导致 switching times increase
Solution Approach 1:
The patent achieves the breakthrough of simultaneously optimizing dielectric anisotropy (Δε ≤ -0.5) and rotational viscosity (γ1 ≤ 165 mPa s) by carefully selecting and combining specific liquid crystal compounds. The molecular structures are chosen to provide strong dipole moments for high dielectric response while maintaining low rotational barriers, resolving the traditional trade-off between these two parameters
Data Source
AI summary
The invention relates to a liquid crystalline medium which contains at least one compound of formula I, where, R1, R1*, L1, L2 and L3 have the same meanings as in Claim 1, as well as to the use thereof for an active matrix display based in particular on the VA, PSA, PS-VA, PA-VA, PALC, FFS, PS FFS, IPS or PS-IPS effect. The invention further relates to compounds of formula I.