Nematic Liquid Crystal Composition for High-Speed VA Displays
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Solution Overview
Problem
Liquid crystal compositions for high-speed response displays, such as televisions, face challenges in achieving sufficiently low viscosity, rotational viscosity, and high elastic constant while maintaining refractive index anisotropy and nematic phase-isotropic liquid phase transition temperature, which are not adequately addressed by existing compositions.
Innovation Solution
A liquid crystal composition combining terphenyl derivatives and fluorobenzene derivatives, with specific compounds represented by general formula (I) and (II), is used, allowing for a content range of 3-45 mass % and including additional components to achieve negative dielectric anisotropy and improved display properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If liquid crystal compounds with substantially zero Δ∈ (compounds C and D) are used, then refractive index anisotropy is maintained, but viscosity is not sufficiently low for high-speed response
Solution Approach 1:
The patent modifies the molecular structure parameters of liquid crystal compounds by introducing specific substituents (fluorine atoms at positions 2 and 3 of phenylene groups, and alkenyl/alkenyloxy groups) to simultaneously achieve the desired refractive index anisotropy and reduced viscosity for high-speed response
Solution Approach 2:
The patent creates a composite liquid crystal composition by combining multiple compounds with different properties: compounds with negative Δ∈ (compounds A and B), compounds with substantially zero Δ∈ (compounds C and D), and the newly disclosed compound (I). This composite approach balances refractive index anisotropy and viscosity requirements
2Speed
If liquid crystal compound (G) and compound (F) are combined, then response speed is improved, but higher response speed is still required
Solution Approach 1:
The patent optimizes molecular parameters by incorporating alkenyl groups (containing C=C bonds) and alkenyloxy groups into the liquid crystal structure, which reduce rotational viscosity and improve response speed while maintaining display quality through controlled molecular interactions
3Speed
If compound represented by formula (I) with low vapor pressure is added to decrease viscosity, then response speed is improved, but content is limited due to low vapor pressure causing volatilization during injection, resulting in high Δn and high viscosity
Solution Approach 1:
The patent modifies the compound (I) structure by introducing fluorine substituents and alkenyl/alkenyloxy groups to optimize the balance between vapor pressure and viscosity, allowing sufficient content (3-45 mass%) to be incorporated without excessive volatilization while achieving the desired low viscosity and high response speed
Solution Approach 2:
The patent uses compound (I) as a model structure with specific substituents that can be systematically modified to create a series of related compounds, all sharing the core beneficial properties of low vapor pressure and appropriate viscosity for high-speed response displays
4Speed
If liquid crystal composition is designed for high-speed response with low viscosity, then response speed is improved, but refractive index anisotropy and nematic phase-isotropic liquid phase transition temperature may decrease
Solution Approach 1:
The patent carefully selects and balances molecular parameters including chain length of alkenyl groups (2-8 carbon atoms), substitution patterns of fluorine atoms, and core structure types to simultaneously achieve low viscosity for high-speed response and maintain adequate nematic phase-isotropic liquid phase transition temperature
Solution Approach 2:
The patent formulates a composite composition combining compounds with different thermal and rheological properties to balance response speed and phase stability, where the synergistic interaction among components maintains nematic phase stability while achieving low overall viscosity
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 composition achieves low viscosity, low rotational viscosity, and high elastic constant without decreasing refractive index anisotropy or nematic phase-isotropic liquid phase transition temperature, resulting in high display quality and response speed for liquid crystal display devices.
Implementation Method 1
a liquid crystal composition which has a negative dielectric anisotropy (Δ∈)
Implementation Method 2
the refractive index anisotropy (Δn) are not decreased
Data Source
AI summary
The present invention provides a liquid crystal composition having a sufficiently low viscosity (η), a sufficiently low rotational viscosity (γ1), a high elastic constant (K33), and a negative dielectric anisotropy (Δ∈) with a high absolute value without decreasing the refractive index anisotropy (Δn) and the nematic phase-isotropic liquid phase transition temperature (Tni); and a liquid crystal display device with a VA mode that uses the liquid crystal composition and has high display quality and high response speed. The liquid crystal display device that uses the liquid crystal composition of the present invention has a distinguished feature of high-speed response and is particularly useful as an active matrix driving liquid crystal display device. The liquid crystal display device is applicable to a VA mode, PSVA mode, PSA mode, IPS mode, or ECB mode liquid crystal display device.