Liquid-Crystalline Medium Composition for Fast FFS Display Response
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Solution Overview
Problem
Existing liquid-crystal displays, particularly in FFS and IPS modes, face challenges with long addressing times, inadequate resistivity, high operating voltages, and insufficient shelf life, along with issues like low elastic constants, high rotational viscosity, and inadequate contrast ratios, which affect image quality and energy efficiency.
Innovation Solution
A liquid-crystalline medium comprising compounds of Formula I and/or L1 and/or L2, with specific radical substitutions, is developed to enhance properties such as high specific resistance, low threshold voltage, fast response times, and improved low-temperature stability, thereby optimizing contrast, brightness, and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional liquid-crystalline compositions are used in FFS and IPS displays, then the displays can operate, but they exhibit long addressing times and high rotational viscosity
Solution Approach 1:
The patent modifies the molecular structure of liquid-crystalline compounds by introducing specific substituent groups (fluoro, chloro, cyano, alkoxy, alkyl groups) at defined positions in the molecular backbone. This changes the physical parameters of the liquid crystal medium, specifically reducing rotational viscosity and improving dielectric properties to achieve faster response times while maintaining stable operation.
Solution Approach 2:
The patent creates composite liquid-crystalline compositions by combining multiple compounds with different molecular structures and properties. The mixture includes core liquid-crystalline compounds with various substituent patterns, designed to achieve synergistic effects that reduce overall rotational viscosity while maintaining or improving other critical parameters like dielectric anisotropy and elastic constants.
2Reliability
If conventional liquid-crystalline compositions are used, then displays can function, but they have inadequate resistivity and require excessively high operating voltages
Solution Approach 1:
The patent introduces specific substituents (particularly fluoro, chloro, and cyano groups) at defined positions in the liquid-crystalline molecular structure to modify electrical parameters. These substitutions increase specific resistivity and optimize dielectric anisotropy, enabling the liquid crystal to respond effectively to lower operating voltages while maintaining stable electrical properties.
Solution Approach 2:
The patent applies different substituent types at specific positions (R1, R2, R3, R4, R5, R6, R7, R8) of the molecular structure to locally optimize different electrical properties. For example, electron-withdrawing groups like fluoro and cyano are placed at strategic positions to enhance resistivity and dielectric response, while maintaining overall molecular symmetry and liquid-crystalline phase stability.
3Loss of time
If conventional liquid-crystalline compositions are used, then displays can operate, but they show disadvantageously long addressing times
Solution Approach 1:
The patent systematically modifies molecular parameters by introducing light substituents (fluoro, chloro, small alkyl groups) and optimizing the core molecular structure to reduce rotational viscosity. This parameter optimization directly accelerates the response time of the liquid crystal molecules to electric fields, reducing addressing times while maintaining other operational parameters within acceptable ranges.
4Use of energy by moving object
If liquid-crystalline media with high dielectric anisotropy are used to reduce operating voltage, then energy efficiency improves, but contrast ratio and image quality may be compromised
Solution Approach 1:
The patent develops composite liquid-crystalline compositions that balance multiple optical and electrical parameters. By combining compounds with different molecular characteristics, the mixture achieves optimal dielectric anisotropy for low-voltage operation while simultaneously maintaining high birefringence and elastic constants necessary for high contrast ratios and superior image quality.
Solution Approach 2:
The patent optimizes multiple parameters simultaneously through molecular design, including dielectric anisotropy, birefringence, elastic constants, and rotational viscosity. The balanced optimization of these parameters ensures that energy efficiency is improved without compromising contrast ratio or image quality, achieving a multi-parameter optimum rather than single-parameter optimization.
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 new liquid-crystalline medium achieves fast response times, excellent low-temperature stability, and improved image quality with high contrast, addressing the limitations of prior art compositions.
Implementation Method 1
Liquid-crystalline materials for IPS displays of this type are described, for example, in EP 3 299 438 A1, DE 10 2009 005747 A1 and DE 195 28 104. Furthermore, so-called 'fringe-field switching' (FFS) displays have been reported... which contain an LC medium with positive dielectric anisotropy
Implementation Method 2
All these modes utilise an electric field which generated substantially perpendicular to the substrates and the liquid-crystal layer... electric fields have a significant component parallel to the liquid-crystal layer... 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 energy efficient 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.