Branched Polymerizable Compounds for PSA Display Alignment
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Solution Overview
Problem
Current PSA displays face issues with inadequate tilt angles, high pretilt angles that deteriorate under voltage stress, residual unpolymerized reactive mesogens causing image sticking, and limited solubility and stability of polymerizable compounds in LC mixtures, leading to reduced reliability and performance.
Innovation Solution
The use of multireactive polymerizable compounds with branched groups, which can polymerize quickly and completely without photoinitiators, reducing pretilt angles and improving solubility and stability, thereby enhancing the voltage holding ratio and reducing image sticking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polymerizable compounds are used in PSA displays, then the alignment layer can provide planar alignment, but high pretilt angles are generated that deteriorate under voltage stress and reduce reliability
Solution Approach 1:
The patent changes the chemical structure parameters of polymerizable compounds by introducing branched alkyl groups at specific positions (e.g., 2,4,6-trimethylbenzylidene group) to modify the polymerization behavior and reduce pretilt angle generation, thereby improving voltage holding ratio and pretilt stability under voltage stress
Solution Approach 2:
The patent creates a composite LC medium system combining conventional LC compounds with specifically designed polymerizable compounds containing branched groups, where the composite formulation achieves both planar alignment and reduced pretilt angles, improving overall display reliability
2Reliability
If conventional polymerizable compounds are used, then alignment can be achieved, but polymerization is incomplete leaving residual unpolymerized species that cause image sticking
Solution Approach 1:
The patent modifies the polymerizable compound structure by adding branched alkyl groups that facilitate more complete polymerization reactions, reducing residual unpolymerized species and preventing image sticking while maintaining efficient polymerization kinetics
Solution Approach 2:
The patent uses polymerizable compounds designed to fully polymerize and remain stable throughout display operation, eliminating the need to deal with residual reactive species that would otherwise cause degradation over time
3Stability of the object's composition
If conventional polymerizable compounds are used, then some alignment function is provided, but solubility in LC mixtures is limited and stability is reduced
Solution Approach 1:
The patent changes the solubility parameters of polymerizable compounds by introducing branched alkyl groups (e.g., 2,4,6-trimethylbenzylidene) that improve compatibility with conventional LC mixtures, enabling complete mixing without precipitation and simplifying the manufacturing process
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 rapid and complete polymerization, achieving lower pretilt angles, improved reliability, and increased voltage holding ratios, while minimizing residual unpolymerized species and maintaining stability under voltage stress.
Implementation Method 1
The polymerizable compounds according to the invention can be polymerised rapidly and completely, in particular by photopolymerisation, very particularly preferably by UV photopolymerisation, without the addition of photoinitiators
Implementation Method 2
a layer of an LC medium which comprises one or more polymerisable compounds according to the invention and one or more liquid-crystalline compounds, in particular in a PSA display, wherein the polymerisable compounds are aligned and form an aligned polymer network which sustains the alignment of the LC molecules
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 PSA ("polymer sustained alignment") type.