Long-UV Polymerizable LC Medium for Stable PSA Display Alignment
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Solution Overview
Problem
Existing LC displays face challenges in achieving high specific resistance, reliability, low threshold voltage, short response times, and stable tilt angles while using longer UV wavelengths for polymerization, especially in PSA and SA modes, which can lead to issues like image sticking and reduced performance parameters.
Innovation Solution
Development of novel polymerizable compounds and LC media that exhibit high UV absorption at longer wavelengths, enabling quick and complete polymerization, stable tilt angles, and minimal residual effects, suitable for use with UV-LED lamps, and maintaining performance across a broad temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If shorter UV wavelengths are used for polymerization, then polymerization speed and efficiency are improved, but reliability of the LC mixture decreases due to reaction with alignment layer polyimide
Solution Approach 1:
The patent modifies the chemical structure of the polymerizable mesogenic compounds by introducing specific substituents (such as fluorine atoms, cyano groups, or alkoxy groups) that shift the UV absorption spectrum to longer wavelengths. This parameter change allows the RMs to be effectively polymerized at wavelengths ≥320 nm, avoiding the harmful reaction with polyimide alignment layers while maintaining adequate polymerization efficiency.
2Reliability
If longer UV wavelengths are used for polymerization, then reliability of LC mixture is improved, but polymerization speed and completeness decrease
Solution Approach 1:
The patent designs polymerizable mesogenic compounds with optimized molecular structures that exhibit strong UV absorption specifically in the 320-380 nm range. By adjusting the chromophore structure and substituent patterns, the absorption coefficient at these longer wavelengths is maximized, enabling fast and complete polymerization even with reduced UV energy, thus resolving the contradiction between wavelength safety and polymerization efficiency.
3Adaptability or versatility
If polymerizable compounds with absorption at longer UV wavelengths are used, then compatibility with UV-LED lamps is improved, but synthesis complexity increases
Solution Approach 1:
The patent develops a series of polymerizable mesogenic compounds based on common core structures (such as cyclohexane, phenyl, or biphenyl rings) that can be systematically modified with standard substituents to achieve the desired UV absorption characteristics. This modular approach allows for relatively straightforward synthesis using established organic chemistry methods, making the compounds practical for industrial production while ensuring compatibility with UV-LED technology.
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 solution provides LC media with high voltage-holding-ratio, tilt stability, and solubility, minimizing production costs and reducing negative effects on LC mixture performance, while ensuring fast polymerization and reliable display operation.
Implementation Method 1
the RMs are then polymerized in situ by UV photopolymerization
Implementation Method 2
polymerizable compounds having absorption in the long UV wavelength range
Data Source
AI summary
A polymerizable compound having absorption in the long UV wavelength range, a liquid-crystal (LC) medium comprising the polymerizable compound, and the use of the compound or LC medium for optical, electro-optical and electronic purposes, in particular in LC displays, especially in LC displays of the PSA (polymer sustained alignment) or SA (self-aligning) mode, an LC display of the PSA or SA mode comprising the compound or LC medium, and a process of manufacturing the LC display.