PSA Liquid Crystal Display with Non-Terminal Double Bond Compounds
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Solution Overview
Problem
Current liquid-crystal (LC) displays, particularly of the VA and OCB types, face challenges such as strong viewing-angle dependence of contrast, long response times, and inadequate voltage holding ratio, which limit their performance in applications like monitors and TV screens, especially when using existing LC mixtures and reactive mesogens.
Innovation Solution
The development of LC displays that incorporate an LC medium comprising alkenyl compounds with non-terminal double bonds, which allows for polymerization with minimal influence on pretilt angle, enabling shorter response times and improved voltage holding ratio without the need for photoinitiators, and featuring a polymerizable component that forms mesogenic or non-mesogenic compounds with specific structural groups for enhanced electrical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional LC mixtures are used in VA displays, then the display achieves basic functionality, but the response times are long and voltage holding ratio is inadequate
Solution Approach 1:
The patent modifies the chemical composition parameters of the LC mixture by incorporating specific compounds with non-terminal double bonds (formula A) and polymerizable compounds (formula I), which changes the electrical properties including response time and voltage holding ratio. This chemical parameter modification enables both improved speed and reliability simultaneously.
Solution Approach 2:
The patent creates a composite LC medium by combining multiple components: conventional LC compounds, compounds of formula A with non-terminal double bonds, and polymerizable compounds of formula I. This composite material approach allows the system to achieve both fast response times and high voltage holding ratios that cannot be obtained with single-component mixtures.
2Reliability
If polymerization is performed with photoinitiators, then polymerization occurs, but the pretilt angle is significantly influenced and electrical properties deteriorate
Solution Approach 1:
The patent removes photoinitiators from the polymerization system entirely. Instead, it uses compounds of formula A with non-terminal double bonds that can undergo polymerization without photoinitiator catalysis. This extraction of the harmful element (photoinitiator) eliminates its negative impact on pretilt angle while still achieving the desired polymerization and voltage holding ratio improvement.
Solution Approach 2:
The patent introduces compounds of formula A as intermediaries that facilitate polymerization without requiring photoinitiators. These compounds act as mediators between the UV light and the polymerizable compounds, enabling controlled polymerization that preserves the pretilt angle while still improving voltage holding ratio.
3Ease of operation
If MVA displays use protrusions on both electrodes, then controlled switching is achieved, but transparency to light is reduced
Solution Approach 1:
The patent removes protrusions from one of the electrodes (typically the color filter electrode), keeping them only on the TFT electrode. This extraction of protrusions from one side maintains the controlled switching capability through the remaining electrode protrusions while significantly improving light transparency by eliminating the obstruction from the other electrode.
4Illumination intensity
If PVA displays use slits on both electrodes, then transparency to light and contrast are improved, but the display becomes more sensitive to mechanical influences
Solution Approach 1:
The patent removes slits from one of the electrodes, keeping the slit structure only on one electrode (typically the TFT electrode). This extraction of slits from both electrodes maintains the transparency and contrast improvements while reducing mechanical sensitivity, as the single-sided slit structure is less vulnerable to mechanical disturbances.
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 results in LC displays with improved specific resistance, low threshold voltages, short response times, high contrast, and wide viewing angles, along with stable voltage holding ratios after UV exposure, addressing the limitations of previous technologies.
Implementation Method 1
The polymerizable component is obtainable by polymerisation of one or more polymerizable compounds between the substrates of the LC cell in the LC medium with application of an electrical voltage
Implementation Method 2
OCB (optically compensated bend) displays are known which are based on a birefringence effect
Implementation Method 3
The LC medium usually has a negative value of the dielectric (DC) anisotropy. On application of an electrical voltage to the electrodes, a realignment of the LC molecules parallel to the electrode surfaces takes place
Data Source
AI summary
The present invention relates to a liquid-crystal (LC) display of the PSA (polymer sustained alignment) type, and to polymerizable compounds and LC media for use in PSA displays.