Liquid-Crystal Medium for VA and IPS Displays
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Solution Overview
Problem
Current liquid-crystal display technologies face challenges in achieving high specific resistance, short response times, and low threshold voltage while maintaining reliability and stability across varying temperatures, especially in VA and IPS displays, due to limitations in dielectric anisotropy and long-term stability of liquid-crystal mixtures.
Innovation Solution
A liquid-crystal medium comprising compounds with negative dielectric anisotropy, stabilizers, and polymerizable compounds is developed, which improves rotational viscosity and elastic constants, ensuring high reliability and low rotational viscosity even after UV exposure, and allows for broad nematic phase ranges and low rotational viscosity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If liquid-crystal mixtures with negative dielectric anisotropy are used to achieve short response times and low threshold voltage, then response time is improved, but long-term stability and reliability deteriorate due to UV exposure and temperature variations
Solution Approach 1:
The patent applies preliminary action by incorporating stabilizers (compounds of formulae S1 and S2) into the liquid-crystal mixture before the display is put into service. These stabilizers are specifically designed to prevent degradation from UV exposure and temperature variations, thereby maintaining reliability while allowing the use of negative dielectric anisotropy compounds for fast response times.
Solution Approach 2:
The patent employs composite materials by creating a liquid-crystal mixture that combines multiple components: compounds with negative dielectric anisotropy (for fast response), stabilizers of formulae S1 and S2 (for UV and thermal stability), and optionally polymerizable compounds (for additional stabilization). This composite approach allows the mixture to achieve both short response times and high long-term stability.
2Use of energy by moving object
If compounds with negative dielectric anisotropy are used to reduce threshold voltage, then threshold voltage is improved, but rotational viscosity increases leading to slower response times
Solution Approach 1:
The patent applies parameter changes by carefully selecting and optimizing the molecular structures of the compounds with negative dielectric anisotropy. The compounds are designed to have specific molecular weights, shapes, and functional groups that minimize rotational viscosity while maintaining high dielectric anisotropy. This allows the achievement of low threshold voltage without sacrificing response speed.
3Reliability
If liquid-crystal mixtures are stabilized against UV exposure and temperature, then reliability is improved, but the complexity of the mixture composition increases
Solution Approach 1:
The patent applies local quality by assigning specific functions to specific components in the mixture: compounds with negative dielectric anisotropy handle the electro-optical performance, stabilizers of formula S1 handle UV stability, stabilizers of formula S2 handle thermal stability, and polymerizable compounds provide additional stabilization. This functional differentiation allows each component to be optimized for its specific role, improving overall reliability while keeping the total complexity manageable.
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 enables liquid-crystal displays with improved response times, high reliability, and stability across extreme temperatures, reducing image sticking and maintaining high VHR values, while allowing for quick polymerization and low pretilt angle generation.
Implementation Method 1
Liquid-crystal display technologies face challenges in achieving high specific resistance, short response times, and low threshold voltage while maintaining reliability and stability across varying temperatures, especially in VA and IPS displays
Implementation Method 2
The principle of electrically controlled birefringence, the ECB effect or also DAP (deformation of aligned phases) effect
Implementation Method 3
allows for broad nematic phase ranges
Data Source
AI summary
The invention relates to a liquid-crystalline medium, in particular based on a mixture of polar compounds, and to the use thereof for an active-matrix display, in particular based on the VA, PSA, PS-VA, PA-VA, PALC, FFS, PS-FFS, IPS or PS-IPS effect.