Bimesogenic Compounds for Flexoelectric Liquid Crystal 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 unfavorable birefringence and dielectric anisotropy, which are not compatible with current LCD driving schemes.
Innovation Solution
The development of bimesogenic compounds with specific structural features, such as certain alkyl and ether-linked mesogenic groups, which induce a second nematic phase in liquid crystal mixtures, optimizing birefringence, dielectric anisotropy, and elastic constants to achieve improved switching angles, response times, and uniform alignment without mechanical shearing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If chiral nematic materials are used for flexoelectric displays, then the display can achieve fast response times, but the driving voltage requirement becomes excessively high
Solution Approach 1:
The patent modifies the chemical composition and structural parameters of the liquid crystal mixture by incorporating specific bimesogenic compounds with optimized molecular structures. This changes the physical parameters of the mixture, including dielectric anisotropy and elastic constants, to reduce the flexoelectric switching voltage while preserving fast response characteristics
Solution Approach 2:
The invention creates a composite liquid crystal system by combining chiral nematic materials with specifically designed bimesogenic compounds. This composite approach allows the mixture to exhibit both fast response times and reduced voltage requirements, overcoming the limitations of pure chiral nematic materials
2Adaptability or versatility
If conventional liquid crystal mixtures are used, then the phase range is sufficient, but the birefringence and dielectric anisotropy are unfavorable for flexoelectric switching
Solution Approach 1:
The patent systematically adjusts the molecular structure parameters of the bimesogenic compounds and their concentration in the mixture to optimize the optical and electrical parameters. This includes tuning birefringence and dielectric anisotropy to achieve superior flexoelectric switching performance while maintaining adequate phase range
Solution Approach 2:
The invention introduces specific bimesogenic compounds with localized functional groups and molecular structures that provide enhanced dielectric anisotropy and birefringence properties in specific regions of the liquid crystal mixture, improving overall switching performance
3Ease of operation
If chiral nematic materials with short pitch are used for uniformly lying helix arrangement, then the display mode is achieved, but the phase range becomes narrow
Solution Approach 1:
The patent develops a composite liquid crystal mixture that combines chiral nematic materials with bimesogenic compounds. This composite formulation broadens the phase range while maintaining the short pitch necessary for uniformly lying helix arrangement, thus preserving alignment uniformity across a wider temperature range
Solution Approach 2:
The invention modifies the pitch parameter and thermal parameters of the liquid crystal mixture through careful selection and combination of components. This allows the mixture to maintain the required short pitch for ULH mode while extending the operational phase 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 compounds enable high switching angles, fast response times, and good contrast at low temperatures, with low melting points and broad chiral nematic phase ranges, making them suitable for flexoelectric displays with improved uniform alignment and reduced voltage requirements.
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, which is equivalent to a cholesteric material
Implementation Method 2
The flexoelectric effect is characterized by fast response times typically ranging from 6 μs to 100 μs. It further features excellent grey scale capability. The field induces a splay bend structure in the director which is accommodated by a tilt in the optical axis
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 compounds of formula (I) wherein R11, R12, MG11, MG12, X11, X12 and Sp1 have the meaning given in claim 1, to the use of these compounds of formula (I) in liquid crystal media and to respective devices comprising a liquid crystal medium according to the present invention and in particular to flexoelectric liquid crystal devices.