Polymerizable Compound for Liquid Crystal Display Stability
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Solution Overview
Problem
Current liquid crystal media for PSA-VA and OCB displays face issues such as high melting point, limited solubility, incomplete polymerization, and susceptibility to UV-induced deterioration, leading to residual images, uneven display, and low voltage holding ratio, which affect the performance and reliability of liquid crystal display devices.
Innovation Solution
A polymerizable compound with a specific molecular structure, characterized by the presence of polymerizable groups and substituents, is introduced to create a liquid crystal medium that exhibits improved solubility, polymerization rate, and stability, reducing the occurrence of defects and enhancing the performance of liquid crystal display devices by ensuring uniform polymer particle formation and maintaining high voltage holding ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polymerizable mesogenic units are used in liquid crystal media, then polymerization can be achieved, but the melting point is high and solubility is limited
Solution Approach 1:
The patent modifies the molecular structure parameters of polymerizable mesogenic units by introducing specific substituents (fluorine atoms, alkyl groups, alkoxy groups) at defined positions. These parameter changes optimize the balance between polymerization reactivity and solubility, lowering the melting point while maintaining polymerization capability. The structural modifications allow the compound to dissolve better in liquid crystal hosts without sacrificing polymerization completeness.
Solution Approach 2:
The patent creates a composite liquid crystal medium by combining the polymerizable mesogenic unit with multiple co-mesogens having different molecular structures and properties. This composite approach improves overall solubility and prevents crystallization while maintaining the polymerization functionality. The mixture of different mesogenic components compensates for the limited solubility of individual polymerizable units.
2Stability of the object's composition
If polymerization is performed in liquid crystal displays, then alignment stability is improved, but residual images and uneven display occur due to incomplete polymerization
Solution Approach 1:
The patent optimizes the polymerizable group selection (acrylate, methacrylate, vinyl groups) and their positioning on the mesogenic core to achieve uniform polymerization. The molecular structure parameters are adjusted to ensure complete polymerization conversion, eliminating residual monomers that cause display defects. The specific structural design promotes uniform cross-linking throughout the liquid crystal medium.
3Adaptability or versatility
If liquid crystal media are used in VA mode displays, then wide viewing angle is achieved, but response time is slow and driving voltage is high
Solution Approach 1:
The patent modifies the molecular structure parameters of the liquid crystal compounds by introducing fluorine substituents and optimizing the mesogenic core structure. These changes reduce molecular weight and increase molecular flexibility, which lowers rotational viscosity. The structural optimization maintains the negative dielectric anisotropy required for VA mode while improving response speed.
4Stability of the object's composition
If liquid crystal media are exposed to UV light for polymerization, then alignment is stabilized, but UV-induced deterioration occurs
Solution Approach 1:
The patent converts the harmful UV effect into a beneficial polymerization process. By incorporating photopolymerizable groups that specifically react to UV light, the previously harmful UV exposure is transformed into a controlled polymerization trigger. The UV light that would otherwise cause deterioration is now used to initiate uniform polymerization, stabilizing the liquid crystal alignment while minimizing degradation through optimized exposure protocols.
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 solution results in a liquid crystal medium with improved solubility, stability, and polymerization characteristics, reducing defective panels and enhancing the performance of liquid crystal display devices by achieving a high voltage holding ratio and preventing demixing at low temperatures, thus improving the overall display quality and reliability.
Implementation Method 1
The liquid crystal medium further comprises a polymerizable compound... subjected to UV irradiation... ensuring uniform polymer particle formation
Implementation Method 2
maintaining high voltage holding ratio... The liquid crystal medium... exhibits improved solubility, polymerization rate, and stability
Data Source
AI summary
Disclosed is a polymerizable compound having a structural formula as represented by the following formula I:The polymerizable compound disclosed in the present invention has a plurality of ring systems, and the entire molecular structure thereof is curved and twisted. The present invention further discloses a liquid crystal medium comprising the polymerizable compound, the polymerizable compound provided by the present invention has an appropriate polymerization rate in the liquid crystal medium, and the liquid crystal medium can be well applied to a PS-(polymer stabilized)- or PSA-(polymer stabilized alignment)-type liquid crystal display device. Further disclosed is a liquid crystal display device prepared from the liquid crystal medium.