Liquid Crystalline Medium for IPS Displays
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Solution Overview
Problem
Current liquid crystal displays, particularly In-Plane Switching (IPS) mode LCDs, face challenges with long response times, high operation voltages, and low resistivity due to the limitations of existing liquid crystalline media, which require improvements in viscosity, dielectric anisotropy, and nematic phase range.
Innovation Solution
A liquid crystalline medium comprising dielectrically positive compounds of specific formulas, along with optional dielectrically neutral components, is developed to achieve improved dielectric anisotropy, rotational viscosity, and nematic phase range, optimizing the medium's composition to enhance display performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional liquid crystalline media are used in IPS displays, then the display can operate, but the response times are unacceptably long
Solution Approach 1:
The patent modifies the molecular structure of liquid crystal compounds by introducing specific chemical groups (cyclohexylidene, fluorine atoms, ester linkages) to change physical parameters such as rotational viscosity and dielectric anisotropy, thereby achieving faster response times while maintaining display performance
Solution Approach 2:
The patent creates a composite liquid crystalline medium by combining multiple compounds with different molecular structures and properties, including dielectrically positive and dielectrically neutral components, to achieve optimal balance between response time, viscosity, and electro-optical performance
2Use of energy by moving object
If liquid crystalline media with higher dielectric anisotropy are used, then operation voltage can be reduced, but specific resistivity decreases detrimentally
Solution Approach 1:
The patent carefully balances dielectric anisotropy within the range of 4-12 by selecting specific molecular structures and substituent groups, achieving sufficiently low operation voltage while maintaining adequate specific resistivity through optimized molecular design rather than maximizing dielectric anisotropy alone
Solution Approach 2:
The patent combines dielectrically positive compounds (for adequate dielectric anisotropy) with dielectrically neutral compounds (for high specific resistivity) in a composite medium, achieving a balance between operation voltage and resistivity that cannot be achieved with single compounds
3Speed
If liquid crystalline media with lower rotational viscosity are used, then response times improve, but the nematic phase range may be reduced
Solution Approach 1:
The patent modifies molecular structure by introducing flexible linkages (ester groups, alkylene chains) and specific ring structures that reduce rotational viscosity while maintaining adequate nematic phase range through balanced molecular rigidity and flexibility
Solution Approach 2:
The patent combines compounds with different phase characteristics and viscosity properties to create a composite medium where the overall nematic phase range is maintained or extended while the average rotational viscosity is reduced for faster response
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 optimized liquid crystalline medium exhibits reduced rotational viscosity, increased dielectric anisotropy, and a wider nematic phase range, leading to faster response times and lower operation voltages, making it suitable for modern display applications.
Implementation Method 1
appropriate birefringence (Δn) and dielectric anisotropy (Δε) should be high enough to allow a reasonably low operation voltage. Preferably Δε should be higher than 4 and very preferably higher than 5
Implementation Method 2
appropriate birefringence (Δn) and dielectric anisotropy (Δε) should be high enough to allow a reasonably low operation voltage
Implementation Method 3
liquid crystalline media with lower viscosities (η), especially with lower rotational viscosities (γ1) are required. The rotational viscosity should be 75 mPa·s or less, preferably 60 mPa·s or less and especially 55 mPa·s or less
Data Source
AI summary
The instant invention relates to dielectrically positive liquid crystalline media comprising a dielectrically positive component, component A, comprising a dielectrically positive compound of formula I wherein the parameters have the meaning given in the specification, and optionally a second dielectrically positive component, component B, comprising one or more dielectrically positive compounds having a dielectric anisotropy of more than 3 and optionally a dielectric neutral component, component C, as well as to liquid crystal displays comprising these media, especially to active matrix displays and in particular to TN and to IPS displays.