Liquid-Crystalline Medium for Fast Response and Low-Temperature Stability
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Solution Overview
Problem
Current liquid-crystal display technologies face challenges in achieving high specific resistance, short response times, and low threshold voltage for generating grey shades, particularly in VA and TN displays, which are essential for high-information displays and television applications, while also requiring stability across extreme temperatures and long operating periods without image sticking.
Innovation Solution
A liquid-crystalline medium comprising specific compounds of formulas I and IA, along with additional compounds like BC, CR, PH-1, PH-2, BF, and BS, which provide negative dielectric anisotropy, low rotational viscosities, and high elastic constants, enabling broad nematic phase ranges, improved low-temperature stability, and short response times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional liquid-crystal compounds are used in VA and TN displays, then the displays can achieve basic electro-optical functionality, but the response times are too long and specific resistance is insufficient for high-information displays and television applications
Solution Approach 1:
The patent applies parameter changes by modifying the molecular structure of liquid-crystal compounds through specific chemical substitutions (fluorine atoms at positions 5 and 6 of the benzene ring, cyano groups at positions 3 and 4, and ester linkages). These structural parameter changes result in compounds with optimized physical parameters including response time, specific resistance, dielectric anisotropy, and rotational viscosity, thereby resolving the contradiction between fast response and stability.
Solution Approach 2:
The patent employs composite materials by creating liquid-crystal compounds that integrate multiple functional moieties within a single molecular structure. The compounds combine benzene rings, ester groups, cyano groups, and fluorine atoms to achieve a synergistic effect that simultaneously provides fast response times and high specific resistance stability, essential for high-information displays and television applications.
2Speed
If liquid-crystal compounds with fast response times are used, then response time improves, but low-temperature stability deteriorates
Solution Approach 1:
The patent uses parameter changes by carefully selecting and positioning functional groups (fluorine atoms at positions 5 and 6, cyano groups at positions 3 and 4) on the benzene ring structure. These parameter changes optimize the balance between molecular mobility (affecting response time) and intermolecular interactions (affecting low-temperature stability), enabling fast response while maintaining stability across extreme temperatures.
3Force
If liquid-crystal compounds with high dielectric anisotropy are used to reduce threshold voltage, then threshold voltage decreases, but rotational viscosity increases leading to longer response times
Solution Approach 1:
The patent applies parameter changes by introducing fluorine atoms at specific positions (5 and 6) on the benzene ring and incorporating cyano groups at positions 3 and 4. These structural modifications independently optimize dielectric anisotropy and rotational viscosity parameters, achieving high dielectric anisotropy for low threshold voltage while maintaining low rotational viscosity for fast response times, thereby resolving the contradiction.
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 proposed liquid-crystalline medium achieves improved rotational viscosities, response times, and low-temperature stability, with high elastic constants and negative dielectric anisotropy, making it suitable for VA, IPS, and FFS displays, particularly for passive matrix applications, and enhancing the reliability and performance of liquid-crystal displays.
Implementation Method 1
electro-optical display elements based on the ECB effect have a homeotropic edge alignment
Implementation Method 2
The principle of electrically controlled birefringence, the ECB effect or also DAP (deformation of aligned phases) effect
Implementation Method 3
The principle of electrically controlled birefringence
Implementation Method 4
values for the dielectric anisotropy of Δε ≤ -0.5
Implementation Method 5
high values for the ratio of the elastic constants K 3 /K 1
Data Source
AI summary
The invention relates to a liquid-crystalline medium which contains at least one compound of the formula I, and at least one compound of the formula in which R1, R1*, R1A, R1A*, L1 and L2 have the meanings indicated in Claim 1, and to the use thereof for an active-matrix display or passive matrix display, for example based on the VA, PSA, PS-VA, PVA, MVA, PM-VA, PALC, FFS, UB-FFS, PS-FFS, IPS or PS-IPS effect.