Polymerisable Compounds for Stable Pretilt Angles in PSA Displays
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Solution Overview
Problem
Current polymer sustained alignment (PSA) displays face issues with inadequate tilt or pretilt angles, voltage holding ratio (VHR), image sticking, high melting points, limited solubility, and increased viscosities, which affect reliability and performance, especially under UV exposure.
Innovation Solution
Development of novel polymerisable compounds with specific structures that enable rapid and complete polymerisation, stable pretilt angles, high VHR values, and improved solubility, which are designed for use in PSA displays and can be photopolymerised without photoinitiators, reducing residual unpolymerised materials and image sticking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polymerisable compounds are used in PSA displays, then the display can be manufactured, but the polymerisation is incomplete and slow, leading to residual unpolymerised materials and image sticking
Solution Approach 1:
The patent modifies the chemical structure of polymerisable compounds by introducing specific radical combinations (aromatic rings with alkoxy/alkyl groups combined with vinyl or cyclohexenyl moieties) to optimize polymerisation kinetics and completeness, eliminating image sticking while maintaining reliability
Solution Approach 2:
The invention creates composite LC media formulations combining multiple polymerisable compounds (Formula I compounds with other vinyl/cyclohexenyl compounds) in specific ratios to achieve synergistic effects that improve both polymerisation completeness and speed
2Reliability
If conventional polymerisable compounds are used in PSA displays, then the display structure is simple, but the pretilt angle is inadequate and voltage holding ratio is poor
Solution Approach 1:
The patent optimizes molecular parameters of polymerisable compounds including aromatic ring substitutions (alkoxy, alkyl groups), vinyl/cyclohexenyl positioning, and molecular weight to achieve optimal pretilt angles and voltage holding ratios while managing structural complexity
3Ease of manufacture
If conventional polymerisable compounds are used in PSA displays, then the manufacturing process is simple, but the compounds have high melting points and limited solubility in LC host mixtures
Solution Approach 1:
The patent adjusts physical parameters of polymerisable compounds by modifying molecular structure (adding flexible alkyl chains, adjusting aromatic ring substitutions) to reduce melting points and enhance solubility in LC host mixtures while maintaining manufacturability
4Productivity
If conventional polymerisable compounds are used in PSA displays, then the display can operate, but the viscosity is increased affecting performance
Solution Approach 1:
The patent optimizes molecular size, shape, and flexibility parameters of polymerisable compounds (using smaller aromatic rings, flexible alkyl chains, and appropriate substitution patterns) to minimize viscosity increase upon polymerisation while maintaining display performance
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 new compounds facilitate quick and complete polymerisation, enhance the stability of pretilt angles, and improve the voltage holding ratio, leading to improved reliability, reduced image sticking, and better performance under UV exposure, while also offering low melting points and increased solubility in LC host mixtures.
Implementation Method 1
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 type
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 type.