Liquid Crystal Medium for Flexoelectric Displays
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Solution Overview
Problem
Current flexoelectric liquid crystal displays face challenges such as high driving voltage requirements, narrow phase ranges of chiral nematic materials, irreversible switching properties, and poor contrast due to unfavourable 'off-state' darkness, which are not compatible with standard LCD driving schemes.
Innovation Solution
A medium comprising at least 60% of compounds of formula I, which include specific alkyl groups and mesogenic groups, is used to improve the alignment and flexoelectric properties, enabling high switching angles, fast response times, and low melting points, with optimized birefringence and dielectric anisotropy for uniform orientation and low voltage operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If chiral nematic materials are used for flexoelectric displays, then fast response times and good viewing angle properties are achieved, but high driving voltage requirements and narrow phase ranges occur
Solution Approach 1:
The patent modifies the chemical structure of liquid crystal compounds by introducing specific mesogenic groups and alkyl chains, which changes the physical parameters (phase range, dielectric anisotropy, birefringence) to achieve low-voltage operation while maintaining fast response times
Solution Approach 2:
The patent uses mixtures of different liquid crystal compounds (chiral nematic materials combined with other mesogenic compounds) to create composite materials that exhibit both narrow phase ranges and low driving voltage requirements, resolving the contradiction between response speed and energy consumption
2Speed
If chiral nematic materials are used for flexoelectric displays, then fast response times are achieved, but irreversible switching properties and poor contrast occur
Solution Approach 1:
The patent optimizes the dielectric anisotropy and elastic constants of the liquid crystal mixture through chemical structure modification, enabling reversible switching behavior while maintaining fast response times and improving contrast ratio
3Adaptability or versatility
If conventional liquid crystal compounds are used, then standard LCD driving schemes are compatible, but uniform alignment and flexoelectric properties are insufficient
Solution Approach 1:
The patent introduces specific mesogenic groups and lateral substituents in the liquid crystal compound structure, which modifies the molecular shape and interaction parameters to achieve superior alignment uniformity and flexoelectric properties while remaining compatible with standard driving schemes
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 medium achieves improved uniform alignment, high switching angles, fast response times, and enhanced contrast at low temperatures, making it suitable for flexoelectric displays with reduced voltage requirements and improved optical performance.
Implementation Method 1
a chiral substance, which is mixed with a nematic material, induces a helical twist transforming the material into a chiral nematic material
Implementation Method 2
If an electrical field is applied to this configuration normal to the helical axis the optical axis is rotated in the plane of the cell... The flexoelectric effect is characterized by fast response times
Implementation Method 3
the optical retardation, i. e. the product of the effective birefringence of the liquid crystal and the cell gap, is selected to be the quarter of the wave length
Data Source
AI summary
The invention relates to a medium comprising at least 60% of one or more compounds of formula (I) wherein R11, R12, MG1 1, MG12 and Sp1 have the meaning given herein below, to the use of such media in liquid crystal devices, in particular in flexoelectric liquid crystal devices, and to a flexoelectric liquid crystal device comprising a liquid crystal medium according to the present invention.