Polymerizable Mesogenic Compounds for PSA Displays
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Solution Overview
Problem
Current liquid-crystal display (LCD) technologies, particularly in polymer sustained alignment (PSA) mode, face issues with high melting points of polymerizable mesogenic compounds, limited solubility, spontaneous crystallization, and uncontrolled polymerization, leading to problems like image sticking, high viscosities, and reduced reliability, especially under UV exposure.
Innovation Solution
The use of polymerizable compounds with an aromatic mesogenic core containing an alkylidene-fluorene group and reactive groups, which facilitate quick and complete UV-photopolymerization at longer wavelengths, reducing tilt angles, image sticking, and residual polymerization issues, while maintaining high reliability and solubility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polymerizable mesogenic compounds are used in PSA displays, then the alignment layer can be formed, but the compounds have high melting points and limited solubility leading to spontaneous crystallization
Solution Approach 1:
The patent modifies the molecular structure of polymerizable mesogenic compounds by introducing specific substituents and adjusting the core structure to reduce melting points while maintaining liquid crystalline properties and polymerizability, thereby preventing spontaneous crystallization during display operation
Solution Approach 2:
The invention develops composite LC media formulations combining multiple components with complementary properties, where the polymerizable mesogenic compounds are integrated with other LC materials to enhance solubility, reduce crystallization tendency, and maintain display performance
2Reliability
If conventional polymerizable compounds are used, then alignment can be sustained, but uncontrolled polymerization occurs leading to image sticking and high viscosities
Solution Approach 1:
The patent incorporates polymerization control mechanisms and stabilizers into the LC medium formulation beforehand, preventing uncontrolled polymerization during storage and display operation, thereby eliminating image sticking while maintaining alignment stability
Solution Approach 2:
The invention implements controlled polymerization through feedback mechanisms where polymerization is triggered only under specific conditions (such as UV irradiation during manufacturing), allowing precise control over when and how polymerization occurs to avoid harmful effects during normal operation
3Reliability
If polymerization is performed to sustain alignment, then alignment stability is improved, but residual polymerization effects and production time increase
Solution Approach 1:
The patent employs periodic or controlled-stage polymerization processes where UV irradiation is applied in specific sequences to achieve complete polymerization for alignment stability while minimizing production time and avoiding residual polymerization effects during display operation
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 fast and stable polymerization, reducing tilt angle generation time, improving voltage-holding ratio, and enhancing display performance with reduced production time and costs, while minimizing residual polymerization effects and image sticking.
Implementation Method 1
facilitate quick and complete UV-photopolymerization at longer wavelengths
Data Source
AI summary
The present invention relates to polymerisable compounds, to processes and intermediates for the preparation thereof, to liquid-crystal (LC) media comprising them, and to the use of the polymerisable compounds and LC media for optical, electro-optical and electronic purposes, in particular in LC displays, especially in LC displays of the polymer sustained alignment (PS, PSA) and self-aligning (SA) type.