Nematic Liquid Crystal Composition for High-Speed IPS Displays
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Solution Overview
Problem
Liquid crystal display devices face challenges in achieving high-speed responsiveness, stability to external stimuli, and optimal display quality, particularly in large-sized displays, due to issues with dielectric anisotropy, viscosity, and the One Drop Fill process, which can result in display defects like ghosting and dropping marks.
Innovation Solution
A liquid crystal composition with positive dielectric anisotropy, comprising specific compounds represented by Formulas (1.1) and (2.1), is developed, which exhibits low viscosity, high specific resistance, and voltage holding ratio, enabling high-speed response and stable production processes, thereby reducing display defects and improving yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a liquid crystal composition showing positive dielectric anisotropy is used in horizontal alignment display modes (TN, STN, IPS), then display functionality is achieved, but achieving high-speed responsiveness requires low rotational viscosity which conflicts with maintaining high dielectric anisotropy and stability
Solution Approach 1:
The patent uses a composite liquid crystal composition containing multiple components: a cyclic carbonate compound (component A), a liquid crystal compound with positive dielectric anisotropy (component B), and a liquid crystal compound with negative dielectric anisotropy (component C). This composite approach allows optimization of multiple properties simultaneously - the cyclic carbonate provides low viscosity for fast response, while the other components contribute to high dielectric anisotropy and thermal stability, resolving the contradiction between speed and reliability.
Solution Approach 2:
The patent specifies precise compositional parameters: component A at 5-50 mass%, component B at 30-70 mass%, and component C at 10-30 mass%. By controlling these parameter ranges, the composition achieves optimal balance between rotational viscosity (for response speed), dielectric anisotropy (for display performance), and thermal stability (for reliability). The specific parameter control resolves the contradiction by finding the optimal operating point.
2Productivity
If the One Drop Fill process is used for filling liquid crystal composition in large-sized display devices, then production efficiency is improved, but display quality deteriorates due to marks and defects caused by dropping
Solution Approach 1:
The patent optimizes the viscosity parameter of the liquid crystal composition by incorporating cyclic carbonate compounds with specific molecular structures. The composition achieves a viscosity range of 10-50 mPa·s at 20°C, which is low enough to enable smooth dropping without marks during the One Drop Fill process, while maintaining high dielectric anisotropy. This parameter optimization resolves the contradiction between production efficiency and display quality.
Solution Approach 2:
The patent introduces a surfactant (component D) at 0.01-5 mass% that locally modifies the surface properties of the liquid crystal composition. This surfactant reduces surface tension and prevents mark formation during dropping, while not affecting the bulk optical and electrical properties. This local modification resolves the contradiction by addressing the dropping issue without compromising display quality.
3Volume of moving object
If liquid crystal composition is used in small-sized display devices with small filling amounts, then device size is reduced, but control of filling amount deviation becomes difficult leading to display defectiveness
Solution Approach 1:
The patent optimizes the viscosity parameter to a specific range (10-50 mPa·s at 20°C) that provides sufficient flow characteristics for accurate dispensing of small amounts. This viscosity optimization ensures that even in small-sized devices with filling amounts of several microliters or less, the liquid crystal can be precisely controlled during the One Drop Fill process, preventing underfilling or overfilling defects.
Solution Approach 2:
The patent introduces a surfactant (component D) as an intermediary that mediates the filling process. The surfactant modifies the wetting and flow characteristics of the liquid crystal composition, enabling precise control of small filling amounts. This intermediary substance allows accurate dispensing in small-sized devices without compromising the bulk properties of the liquid crystal.
4Use of energy by moving object
If liquid crystal composition requires high dielectric anisotropy for low-voltage driving, then driving voltage is reduced, but viscosity tends to increase which conflicts with high-speed responsiveness requirement
Solution Approach 1:
The patent uses a composite composition where component B (liquid crystal compound with positive dielectric anisotropy) provides high dielectric anisotropy for low-voltage driving, while component A (cyclic carbonate compound) provides low viscosity for fast response. The synergistic combination of these components resolves the contradiction between reducing driving voltage and maintaining high-speed responsiveness.
Solution Approach 2:
The patent controls the dielectric anisotropy parameter to be +5.0 or higher while maintaining viscosity in the range of 10-50 mPa·s at 20°C. By precisely controlling these parameter ranges through compositional optimization, the patent achieves both low-voltage driving (enabled by high dielectric anisotropy) and high-speed response (enabled by low viscosity).
Data Source
AI summary
The liquid crystal composition of the present invention is used for liquid crystal display devices of an IPS mode, a TN mode, and the like that have a high response speed and do not easily cause display defectiveness such as ghosting or dropping marks. The liquid crystal composition contains a component which is a dielectrically positive component containing a dielectrically positive compound and a dielectrically neutral component which exhibits dielectric anisotropy greater than −2 and smaller than +2. The liquid crystal composition has excellent properties in which the composition forms a liquid crystal phase in a wide temperature range, has a low viscosity, dissolves excellently at a low temperature, has a high degree of specific resistance and voltage holding ratio, and is stable with respect to heat or light.