Polymerizable LC Medium for Long-Wavelength UV Alignment Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing LC displays face challenges in achieving high specific resistance, wide working-temperature range, short response times, low threshold voltage, high tilt stability, and reliability, especially when exposed to longer UV wavelengths, which can degrade the alignment layers and reduce reliability.
Innovation Solution
Development of LC media comprising specific polymerizable compounds with negative dielectric anisotropy, formulated with compounds of formulas IA and IB, allowing for fast polymerization and stable tilt angle generation, even at longer UV wavelengths, and enhancing solubility and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If shorter UV wavelengths are used to polymerize RMs, then polymerization efficiency is improved, but reliability of the LC medium decreases due to reaction with polyimide alignment layer
Solution Approach 1:
The patent changes the wavelength parameter of UV light from shorter wavelengths (e.g., 300-320nm) to longer wavelengths (e.g., 350-400nm) for polymerization. This parameter change allows efficient polymerization of RMs while avoiding the harmful reaction with polyimide alignment layer that occurs at shorter wavelengths, thus resolving the contradiction between polymerization efficiency and reliability.
2Reliability
If longer UV wavelengths are used to protect alignment layer, then reliability is improved, but polymerization efficiency of RMs decreases
Solution Approach 1:
The patent introduces a photoinitiator as an intermediary substance that absorbs longer wavelength UV light (350-400nm) and converts it to shorter wavelength radiation or chemical energy that can effectively initiate RM polymerization. This intermediary enables the use of longer UV wavelengths for polymerization while maintaining high polymerization efficiency and protecting the alignment layer from damage.
3Speed
If highly polar LC compounds with high dielectric constant are used to reduce response time, then response time is improved, but reliability of LC medium decreases
Solution Approach 1:
The patent optimizes the dielectric constant parameter of LC compounds to achieve a balanced value rather than maximizing it. By selecting LC compounds with moderate dielectric constants and optimizing their composition ratios, the patent achieves sufficiently fast response times while maintaining high reliability and stability of the LC medium, avoiding the degradation issues associated with highly polar compounds.
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 LC media exhibit high specific resistance, fast response times, low threshold voltage, and improved reliability, with reduced image sticking and ODF mura, enabling energy-efficient displays with minimal production costs.
Implementation Method 1
After filling the LC medium into the display the RMs are then polymerized in situ by UV photopolymerization, while a voltage is applied to the electrodes of the display.
Implementation Method 2
LC media comprising polymerizable compounds with negative dielectric anisotropy, formulated with compounds of formulas IA and IB, allowing for fast polymerization and stable tilt angle generation
Implementation Method 3
a small amount, typically 0.1 to 2.5 %, of a self alignment (SA) additive is added to the LC medium, which induces the desired alignment, for example homeotropic or planar alignment, in situ by a self assembling mechanism
Data Source
AI summary
The present invention relates to a liquid-crystal (LC) medium comprising polymerizable compounds, to its use 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, to an LC display of the PSA or SA mode comprising the LC medium, and to a process of manufacturing the LC display.