Liquid-Crystal Medium Composition for Fast, Reliable VA and FFS Switching
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Solution Overview
Problem
Existing liquid crystal (LC) media with negative dielectric anisotropy in VA and FFS displays suffer from reduced reliability, high viscosity, slow switching times, and issues like image sticking and low voltage holding ratio (VHR) due to interactions with alignment layers, especially under UV exposure.
Innovation Solution
A liquid crystal medium comprising compounds of specific formulas, including high polar and high birefringence molecules, which are combined to reduce viscosity, enhance switching speed, and improve reliability by minimizing interactions with alignment layers, thereby maintaining high VHR and reducing image sticking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If LC media with negative dielectric anisotropy are used in VA and FFS displays, then transmission and viewing angle are improved, but reliability and voltage holding ratio deteriorate due to interactions with alignment layers
Solution Approach 1:
The patent modifies the chemical composition parameters of the LC medium by incorporating specific compounds (cyclohexyl benzoate, cyclohexyl cyclohexanecarboxylate, phenyl cyclohexyl benzoate, phenyl cyclohexyl cyclohexanecarboxylate) with controlled weight ratios to achieve negative dielectric anisotropy while maintaining high voltage holding ratio and reliability, resolving the contradiction between transmission improvement and reliability deterioration
Solution Approach 2:
The patent creates a composite LC medium formulation combining multiple compounds with different molecular structures and properties (cyclohexane rings, ester groups, aromatic moieties) to achieve synergistic effects that simultaneously provide negative dielectric anisotropy for improved transmission and high stability for maintained reliability
2Ease of manufacture
If conventional LC media are used, then manufacturing is simpler, but switching times are slow due to high viscosity
Solution Approach 1:
The patent adjusts the viscosity parameter of the LC medium by selecting compounds with specific molecular weights and structures (cyclohexyl rings, ester linkages) that provide optimal flow characteristics, achieving fast switching times while maintaining manufacturability through conventional mixing processes
3Shape
If LC media with negative dielectric anisotropy are used, then director orientation is improved, but image sticking occurs due to UV exposure interactions
Solution Approach 1:
The patent incorporates UV absorbers and stabilizers as additives in the LC medium that sacrificially absorb UV radiation and prevent degradation of the main LC compounds, thereby preventing image sticking while maintaining the desired director orientation properties
Solution Approach 2:
The patent introduces UV absorbers and stabilizers as intermediary substances that mediate between the harmful UV radiation and the LC molecules, protecting the LC medium from UV-induced degradation and image sticking while allowing the negative dielectric anisotropy to provide improved director orientation
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 proposed LC medium achieves fast switching times, high reliability, and improved VHR even under UV exposure, enabling energy-efficient displays with reduced image sticking and enhanced performance across various temperature ranges.
Implementation Method 1
In the switched-off state, the molecules of the LC layer are aligned perpendicular to the electrode surfaces (homeotropically) or have a tilted homeotropic alignment
Implementation Method 2
On application of a voltage to the two electrodes, a realignment of the LC molecules parallel to the electrode surfaces takes place
Implementation Method 3
FFS displays usually contain an LC medium with positive dielectric anisotropy, and an alignment layer, usually of polyimide, which provides planar alignment to the molecules of the LC medium
Implementation Method 4
A strong, so-called 'fringe field' is thereby generated, i.e. a strong electric field close to the edge of the electrodes, and, throughout the cell, an electric field which has both a strong vertical component and also a strong horizontal component
Implementation Method 5
the LC medium usually has a negative value of the dielectric anisotropy (Δε)
Implementation Method 6
FFS displays usually contain an LC medium with positive dielectric anisotropy
Implementation Method 7
high birefringence molecules
Data Source
AI summary
The present invention relates to a liquid-crystal (LC) medium or LC material based on a mixture of polar compounds, to its use for optical, electro-optical and electronic purposes, in particular in LC displays, especially in LC displays of the vertically aligned mode and/or the fringe-field switching mode, to an LC display of the vertically aligned mode and/or the fringe-field switching mode comprising the LC medium, especially an energy-saving LC display and to a process of manufacturing the LC display.