Liquid-Crystal Medium for PSA Displays
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Solution Overview
Problem
Conventional liquid-crystal (LC) media in LC displays, including polymer sustained alignment (PSA) displays, face issues such as high viscosities leading to long switching times, reliability concerns due to UV exposure, and the occurrence of 'mura' (image defects) during the one drop filling process, while also requiring improved viewing angles, contrast, and brightness.
Innovation Solution
Development of novel LC media comprising reactive mesogens (RMs) with specific chemical structures that enable high transmittance, low threshold voltages, rapid polymerization, and stability, including compounds of formulas I, IIBa, IIDa, and III, which are designed to reduce rotational viscosity and enhance UV absorption, allowing for quick and complete polymerization and improved alignment stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional LC media are used in PSA displays, then the display can operate, but high viscosities cause long switching times
Solution Approach 1:
The patent modifies the chemical structure of LC media by incorporating specific compounds (formulae I, IIBa, IIDa, III) that change the physical parameters of the medium, specifically reducing rotational viscosity while maintaining liquid crystalline properties, thereby achieving fast switching times
Solution Approach 2:
The invention creates a composite LC medium by combining multiple compounds with specific functional groups and molecular structures, where the synergistic effect of these compounds reduces overall viscosity while preserving the necessary optical and electrical properties for display operation
2Reliability
If conventional LC media are used, then the display can function, but reliability deteriorates due to UV exposure
Solution Approach 1:
The patent introduces UV-absorbing compounds into the LC medium that convert harmful UV radiation into beneficial effects by absorbing the energy and preventing degradation, thereby improving reliability under UV exposure conditions
Solution Approach 2:
The invention modifies the chemical composition parameters of the LC medium by adding specific UV-stabilizing compounds, changing the optical and chemical properties to resist UV-induced degradation and improve long-term stability
3Manufacturing precision
If conventional LC media are used, then the display can operate, but 'mura' (image defects) occur during the one drop filling process
Solution Approach 1:
The patent adjusts the rheological parameters of the LC medium, specifically modifying viscosity and flow characteristics to enable uniform filling during the one drop filling process, preventing formation of mura defects and achieving homogeneous LC layer distribution
4Illumination intensity
If LC media with high transmittance are used, then brightness improves, but viewing angle dependence of contrast increases
Solution Approach 1:
The invention creates a composite LC system combining materials with complementary properties, where the synergistic interaction achieves both high transmittance and wide viewing angle independence by balancing the optical characteristics of individual components
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 new LC media exhibit improved transmission, high voltage-holding ratios, fast switching times, and enhanced reliability, particularly under UV exposure, while minimizing 'mura' and image sticking, thus addressing the limitations of conventional LC media in PSA displays.
Implementation Method 1
The invention relates to liquid-crystal (LC) media and to the use of the LC media for optical, electro-optical and electronic purposes... comprising reactive mesogens (RMs) with specific chemical structures that enable high transmittance, low threshold voltages, rapid polymerization
Implementation Method 2
The LC cell of a VA display contains a layer of an LC medium between two transparent electrodes, where the LC medium usually has a negative dielectric anisotropy. On application of an electrical voltage to the two electrodes, a realignment of the LC molecules parallel to the electrode surfaces takes place
Implementation Method 3
compounds of formulas I, IIBa, IIDa, and III, which are designed to reduce rotational viscosity and enhance UV absorption
Data Source
AI summary
The present invention relates to a liquid crystal medium comprising a) one or more compounds of formula I b) one or more compounds of the formula IIBa and c) one or more compounds of the formula IIDa as defined in claim 1, and to the use thereof for optical, electro-optical and electronic purposes, in particular in LC displays, especially in IPS, FFS, VA or PS-VA displays.