Halogen-Substituted Terphenyl Compounds for PSA Display Alignment
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Solution Overview
Problem
Current liquid crystal displays, particularly PSA displays, face challenges such as insufficient tilt angle, high rotational viscosity, inadequate Voltage Holding Ratio (VHR), and issues like 'image sticking' due to residual unpolymerized reactive mesogens, which affect contrast, luminance, and switching times.
Innovation Solution
The use of polymerizable compounds with a terphenyl group substituted by halogen atoms, which allows for rapid and complete polymerization without photoinitiators, reducing residual unpolymerized materials and improving electro-optical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polymerizable compounds are used in PSA displays, then polymerization can occur, but the polymerization is incomplete and residual unpolymerized materials remain causing image sticking
Solution Approach 1:
The patent modifies the molecular structure of polymerizable compounds by introducing specific groups (cyano, fluorine, chlorine) and adjusting the ratio of reactive mesogen to non-reactive mesogen (0.1-10% by weight). These parameter changes enable complete polymerization without residual monomers, eliminating image sticking while maintaining display performance.
2Object-generated harmful factors
If polymerizable compounds with high reactivity are used to achieve complete polymerization, then image sticking is reduced, but the pretilt angle control and electro-optical properties may be compromised
Solution Approach 1:
The patent introduces different functional groups at specific positions of the polymerizable compound molecule. The cyano group at the terminal position provides high polymerization reactivity, while fluorine or chlorine substituents on the aromatic ring maintain proper pretilt angle control. This local differentiation of molecular properties allows simultaneous achievement of complete polymerization and precise orientation control.
Solution Approach 2:
The patent creates a composite liquid crystal system combining reactive mesogen (containing polymerizable group), non-reactive mesogen, and specific additives. This composite formulation balances polymerization reactivity with electro-optical performance, ensuring complete curing without compromising pretilt angle or contrast ratio.
3Productivity
If the polymerization is made faster to improve production efficiency, then productivity increases, but the control over pretilt angle and switching times may be affected
Solution Approach 1:
The patent uses polymerizable compounds with specific molecular structures (terminal cyano group, aromatic substituents) that enable rapid polymerization kinetics. The high reactivity allows complete polymerization in shorter exposure times, improving productivity while the controlled molecular architecture ensures that switching times remain within acceptable ranges for display operation.
4Ease of manufacture
If conventional liquid crystal compositions are used, then the display can be manufactured, but the contrast ratio and luminance are insufficient
Solution Approach 1:
The patent formulates a composite liquid crystal composition including reactive mesogen with specific functional groups, non-reactive mesogen, and optimized ratios (0.1-10% reactive component). This composite system achieves superior contrast ratio and luminance while remaining compatible with standard PSA display manufacturing processes, thus improving both performance and manufacturability.
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
This approach enables quicker setting of a low pretilt angle, reduces 'image sticking', and enhances display performance by improving contrast, luminance, and switching times while maintaining high VHR and temperature stability.
Implementation Method 1
rapid and complete polymerization without photoinitiators
Implementation Method 2
OCB displays ('optically compensated bend') are known, which are based on a birefringence effect
Implementation Method 3
the FK medium typically has a negative value of dielectric (DK) anisotropy
Data Source
AI summary
The present invention relates to polymerizable compounds, to methods and intermediate products for the production thereof, and to the use thereof for optical, electro-optical, and electronic purposes, in particular in liquid crystal (LC) media and liquid crystal displays, above all in liquid crystal displays of the PS or PSA type ("polymer sustained" or "polymer sustained alignment").