Nematic Liquid Crystal Composition for VA Displays
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Solution Overview
Problem
Current liquid crystal compositions for VA-type displays face challenges in achieving a negative dielectric constant anisotropy with low viscosity without increasing refractive index anisotropy, which limits response speed and voltage-holding ratio, especially at high temperatures.
Innovation Solution
A nematic liquid crystal composition comprising specific compounds represented by general formulas (I) and (II), which include alkenyl and alkenyloxy groups, is developed to achieve a negative dielectric constant anisotropy while maintaining refractive index anisotropy, thereby enhancing response speed and voltage-holding ratio without reducing the cell gap.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If liquid crystal compounds with 2,3-difluorophenylene structure are used to achieve negative dielectric constant anisotropy, then voltage-holding ratio is improved, but viscosity increases and response speed deteriorates
Solution Approach 1:
The patent modifies the molecular structure parameters of liquid crystal compounds by introducing specific substituents (alkyl, alkoxy, alkenyl groups) at defined positions (R1-R6) on the 2,3-difluorophenylene core. This systematic parameter change allows optimization of the balance between dielectric constant anisotropy and viscosity, achieving both improved voltage-holding ratio and maintained response speed through precise structural control.
Solution Approach 2:
The patent creates composite liquid crystal compositions by combining multiple compounds with different molecular structures and properties. This composite approach allows the formulation of compositions that simultaneously achieve negative dielectric constant anisotropy for improved voltage-holding ratio while maintaining low viscosity for fast response speed, overcoming the limitations of single-compound systems.
2Speed
If cell gap is reduced to achieve quick responsiveness, then response speed is improved, but refractive index anisotropy adjustment becomes difficult and manufacturing precision requirements increase
Solution Approach 1:
Instead of relying solely on reducing cell gap to improve response speed, the patent changes the material parameters by developing liquid crystal compounds with optimized refractive index anisotropy and viscosity. This allows achieving fast response through material property optimization rather than extreme cell gap reduction, thereby maintaining manufacturing feasibility and reducing precision requirements.
3Speed
If liquid crystal compositions with low viscosity are developed to improve response speed, then response speed is improved, but dielectric constant anisotropy may be compromised and voltage-holding ratio deteriorates
Solution Approach 1:
The patent systematically modifies molecular structure parameters including substituent types (alkyl, alkoxy, alkenyl), their positions (R1-R6), and chain lengths to independently optimize viscosity and dielectric constant anisotropy. This enables achieving low viscosity for fast response while maintaining negative dielectric constant anisotropy for improved voltage-holding ratio, resolving the trade-off between speed and reliability.
Solution Approach 2:
The patent formulates composite liquid crystal compositions combining multiple compounds with complementary properties. This allows achieving both low viscosity for fast response and negative dielectric constant anisotropy for high voltage-holding ratio, as the composite system can balance the properties of individual components to satisfy both requirements simultaneously.
4Reliability
If compounds with 1-hydroxy-2,3-difluoro-4-substituted benzene structure are used, then negative dielectric constant anisotropy is achieved, but viscosity remains high and response speed is insufficient for high-speed displays
Solution Approach 1:
The patent modifies the 1-hydroxy-2,3-difluoro-4-substituted benzene structure by introducing specific substituents (alkyl, alkoxy, alkenyl groups) at positions R1-R6. This parameter change optimizes the molecular properties to reduce viscosity while preserving the negative dielectric constant anisotropy, thereby improving response speed for high-speed display applications.
Solution Approach 2:
The patent creates composite liquid crystal compositions using compounds based on the 1-hydroxy-2,3-difluoro-4-substituted benzene structure combined with other complementary compounds. This composite approach enables achieving both negative dielectric constant anisotropy for voltage-holding improvement and reduced viscosity for enhanced response speed, overcoming the limitations of single-compound systems.
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 provides a liquid crystal display element with improved quick responsiveness and high voltage-holding ratio even at high temperatures, suitable for VA, ECB, and IPS types, while maintaining low viscosity and refractive index anisotropy.
Implementation Method 1
liquid crystal materials having a negative dielectric constant anisotropy (Δ∈) are used
Implementation Method 2
the product (Δn×d) of the refractive index anisotropy (Δn) and the cell gap (d)
Data Source
AI summary
A nematic liquid crystal composition of the present invention includes 10 to 80% by mass of either one or at least two compounds represented by general formula (I) as a first component; and 20 to 70% by mass of either one or at least two compounds represented by general formula (II) as a second component, wherein a dielectric constant anisotropy is negative.The use of this nematic liquid crystal composition can provide a highly reliable liquid crystal display element capable of maintaining a high voltage-holding ratio even in a high temperature region, and achieving quick responsiveness without reducing the cell gap.