Nematic Liquid Crystal Composition for Fast Response and Stability
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Solution Overview
Problem
Liquid crystal compositions for display elements face challenges in maintaining stability against heat and light while achieving low viscosity, wide temperature range, high specific resistance, and high voltage holding ratio, which leads to issues like image sticking and drop marks in large display sizes.
Innovation Solution
A nematic liquid crystal composition combining specific compounds with negative dielectric anisotropy, formulated with specific alkyl and alkenyl groups, and fluorine atoms, to achieve low viscosity, good solubility, and high stability, preventing display defects like image sticking and drop marks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If liquid crystal compounds with large Δn are used to reduce cell gap and achieve high-speed response, then response speed is improved, but stability against light and heat decreases
Solution Approach 1:
The patent uses composite liquid crystal compositions containing multiple compounds including cyclic carbonate compounds, cyclic carboxylate compounds, and compounds with specific molecular structures (formulae I-1 to I-3 and II). This composite approach allows achieving both high Δn for fast response and sufficient stability against light and heat through synergistic effects of different components.
Solution Approach 2:
The patent optimizes specific physical parameters of the liquid crystal compounds including Δn (birefringence), viscosity (η), and rotational viscosity (γ1). By carefully selecting compounds with specific molecular structures and adjusting their ratios, the composition achieves Δn≥0.10, η≤25 mPa·s, and γ1≤120 mPa·s, balancing response speed and stability.
2Reliability
If antioxidants are added to improve stability against heat, then stability is improved, but display quality and voltage holding ratio are not sufficiently maintained
Solution Approach 1:
The patent removes or minimizes the use of traditional antioxidants that cause display defects. Instead of adding antioxidants as separate components, the invention achieves stability through the intrinsic properties of the carefully selected liquid crystal compound composition itself, eliminating the need for stabilizing additives that compromise display quality.
Solution Approach 2:
The patent changes the chemical composition parameters by selecting specific stable liquid crystal compounds (cyclic carbonates, cyclic carboxylates, and compounds of formulae I-1 to I-3 and II) that inherently provide thermal stability without requiring antioxidants. The composition achieves high voltage holding ratio (≥90% at 60°C) and display quality through this parameter optimization.
3Speed
If monomer is added and cured to form pre-tilt angle and improve responsiveness, then responsiveness is improved, but drop marks are generated and yield decreases
Solution Approach 1:
The patent eliminates or minimizes the use of polymerizable monomers that cause drop marks during the one-drop-fill process. By achieving the desired pre-tilt angle and responsiveness through the liquid crystal compound composition itself and surface treatment, the invention avoids adding monomer components that would create display defects and reduce yield.
4Productivity
If liquid crystal composition is dropped on substrate using one-drop-fill method, then productivity is improved, but drop marks are formed and display quality decreases
Solution Approach 1:
The patent changes the physical parameters of the liquid crystal composition including viscosity (η≤25 mPa·s) and surface tension characteristics to enable smooth spreading and elimination of drop marks during the one-drop-fill process. The optimized composition flows and levels out properly on the substrate, maintaining high display quality while preserving the productivity benefits of the one-drop-fill method.
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 ensures high-speed response and suppresses display defects, providing stable performance against heat and light, suitable for large display elements like VA-type and PSVA-type liquid crystal display elements.
Implementation Method 1
a nematic liquid crystal composition containing, as a first component, at least one compound selected from the group consisting of compounds represented by general formulae (I-1) to (I-3)... wherein a dielectric anisotropy (Δ∈) at 25° C. is −2.0 or less
Implementation Method 2
it is also necessary to control the Δn of a liquid crystal composition to be in an appropriate range in accordance with a cell gap
Data Source
AI summary
There is provided a nematic liquid crystal composition that exhibits a negative dielectric anisotropy (Δ∈), the liquid crystal composition being useful as a liquid crystal display material, and a liquid crystal display element using the same. The liquid crystal composition has a large absolute value of the dielectric anisotropy thereof and a low viscosity. The liquid crystal composition can provide a liquid crystal display element which has a high contrast, high-speed responsiveness, and good display quality in which image sticking and display defects are not generated. The liquid crystal display element using the liquid crystal composition is a useful display element which realizes both high-speed response and suppression of display defects. In particular, the liquid crystal display element is useful as a liquid crystal display element for active-matrix driving, and can be applied to, for example, a VA-type or PSVA-type liquid crystal display element.