Bimesogenic Compounds for Fast Flexoelectric LCD Response
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Solution Overview
Problem
Current liquid crystal display technologies using flexoelectric modes face challenges such as high driving voltage requirements, narrow phase ranges, irreversible switching properties, and inadequate contrast due to non-uniform orientation and high voltage needs, which are incompatible with standard LCD driving schemes.
Innovation Solution
Development of bimesogenic compounds with specific molecular structures that can be incorporated into liquid crystal media to enhance flexoelectric properties, allowing for high switching angles, fast response times, and improved temperature stability without mechanical shearing, and providing a broad chiral nematic phase range and low melting points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If flexoelectric liquid crystal modes are used to achieve fast response times and good viewing angle properties, then response time is improved, but driving voltage becomes excessively high and incompatible with standard LCD driving schemes
Solution Approach 1:
The patent modifies the physical and chemical parameters of the liquid crystal material by introducing bimesogenic compounds with specific molecular structures. This changes the material's flexoelectric coefficients and elastic constants, enabling fast response times at reduced driving voltages compatible with standard LCD drivers
Solution Approach 2:
The invention uses composite liquid crystal compositions containing bimesogenic compounds combined with chiral dopants and nematic hosts. This composite approach synergistically enhances flexoelectric properties while maintaining low driving voltage requirements and fast response characteristics
2Speed
If chiral substances are added to induce short pitch for uniformly lying helix arrangement, then flexoelectric effect is enhanced, but phase range becomes narrow and temperature stability deteriorates
Solution Approach 1:
The bimesogenic compounds are designed with specific molecular parameters including spacer length, terminal groups, and core structures that simultaneously optimize pitch length, phase range, and temperature stability. By adjusting these parameters, the patent achieves short pitch for strong flexoelectric effect while maintaining broad phase ranges
Solution Approach 2:
The liquid crystal composition combines bimesogenic compounds with chiral dopants and nematic host materials in optimized ratios. This composite formulation broadens the phase range and improves temperature stability while maintaining the short pitch necessary for strong flexoelectric effect
3Device complexity
If conventional liquid crystal materials are used in flexoelectric modes, then material simplicity is maintained, but alignment becomes non-uniform and contrast is inadequate
Solution Approach 1:
The bimesogenic compounds possess specific molecular parameters including dipole moments, elastic constants, and flexoelectric coefficients that are optimized to achieve uniform alignment. The molecular structure parameters are tuned to enhance interaction with alignment layers and improve director uniformity across the display cell
Solution Approach 2:
The patent replaces mechanical shearing processes with electric field-based alignment methods. The bimesogenic compounds respond to electric fields during the alignment process, enabling uniform orientation without mechanical contact, thereby improving alignment uniformity and eliminating associated defects
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 bimesogenic compounds enable flexible tuning of the working temperature range, achieve high switching angles, and provide fast response times and good contrast at low temperatures, while ensuring uniform alignment and reduced rotational viscosity, thus addressing the limitations of existing flexoelectric liquid crystal displays.
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
When an electric field is applied to this configuration normal to the helical axis the optical axis is rotated in the plane of the cell... The applied electric field can induce 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 given wavelength
Data Source
AI summary
The invention relates to bimesogenic compounds of formula (I), wherein R11, R12, MG1, MG2, X11, X12 and Sp1 have the meaning given in claim 1, to the use of bimesogenic compounds of formula (I) in liquid crystal media and in particular to flexoelectric liquid crystal devices comprising a liquid crystal medium according to the present invention.