Fluorophenyl Cyclohexyl Liquid Crystal for VA Displays
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Solution Overview
Problem
Conventional liquid crystal compounds with negative dielectric anisotropy have high rotational viscosity and low refractive index anisotropy, limiting their suitability for vertical alignment liquid crystal displays, which require faster response times, broader nematic temperature ranges, and optimal refractive index anisotropy.
Innovation Solution
A liquid crystal compound with a specific molecular structure, including a combination of alkyl and fluorine-substituted phenylene or cyclohexylene rings, is developed to achieve high dielectric anisotropy, refractive index anisotropy, and broad nematic temperature range, along with a composition comprising primary, secondary, and tertiary liquid crystal compounds to optimize properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional liquid crystal compound with a 2-3-difluorophenyl group is used, then good light and heat stability is achieved, but rotational viscosity is relatively high and refractive index anisotropy is low
Solution Approach 1:
The patent changes the molecular structure parameters by replacing the conventional 2-3-difluorophenyl group with a 2-fluorophenyl group combined with a cyclohexyl group. This structural parameter change simultaneously improves response time (reduces rotational viscosity) while maintaining light and heat stability, resolving the technical contradiction between reliability and speed.
Solution Approach 2:
The patent creates a composite molecular structure by combining a 2-fluorophenyl group with a cyclohexyl group in a specific configuration. This composite structure integrates the beneficial properties of both groups: the fluorophenyl provides dielectric anisotropy and stability, while the cyclohexyl group reduces rotational viscosity and improves response time, thereby resolving the contradiction between stability and speed.
2Reliability
If a conventional liquid crystal compound with a 2-3-difluorophenyl group is used, then good light and heat stability is achieved, but refractive index anisotropy is low
Solution Approach 1:
The patent changes the molecular structure parameters by introducing a cyclohexyl group with specific substituent patterns that enhance refractive index anisotropy. This parameter change increases Δn while maintaining the light and heat stability provided by the fluorophenyl group, resolving the contradiction between reliability and illumination intensity properties.
3Temperature
If the crystal-to-nematic transition temperature is lowered and nematic-to-liquid transition temperature is increased to achieve a broad nematic temperature range, then temperature range is improved, but molecular structure complexity increases
Solution Approach 1:
The patent optimizes the molecular structure parameters by carefully selecting the combination of fluorophenyl and cyclohexyl groups with specific substituent positions and types. This parameter optimization achieves a broad nematic temperature range while keeping the molecular structure relatively simple and suitable for conventional manufacturing processes, resolving the contradiction between temperature range and structural complexity.
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 developed liquid crystal compound and composition exhibit improved dielectric anisotropy, refractive index anisotropy, and nematic temperature range, enhancing their suitability for vertical alignment liquid crystal displays with faster response times and improved stability.
Implementation Method 1
A liquid crystal compound used in such a vertical alignment liquid crystal display unit should have negative dielectric anisotropy (Δ∈), good light and heat stability, a broad nematic temperature range, fast response time, etc.
Implementation Method 2
if a liquid crystal compound has an increased refractive index anisotropy (Δn), a cell gap for filling with liquid crystal can be reduced
Data Source
AI summary
A liquid crystal composition includes a liquid crystal compound having a formula (I), where R1 and R2 are independently selected from the group consisting of H, C1-C10 alkyl, C2-C10 alkenyl, C1-C10 alkoxyl, C2-C10 alkenyloxy, C1-C10 ether, C1-C10 aldehyde, C1-C10 ketone, and C1-C10 ester; A is selected from the group consisting ofand X1, X2, X3 and X4 are independently selected from the group consisting of H, halogen group, —CF3, —CHF2, —CH2F, —OCF3, —OCHF2 and —OCH2F, at least one of X1, X2, X3 and X4 being halogen group, —CF3, —CHF2, —CH2F, —OCF3, —OCHF2 or —OCH2F.