Composite Liquid Crystal Composition for Low Voltage Display Operation
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Solution Overview
Problem
The existing polymer dispersed liquid crystal display elements face challenges in maintaining high birefringence index and photostability while keeping driving voltage low, as increasing the content of liquid crystal compounds with biphenyl or naphthalene skeletons can reduce stability and increase driving voltage.
Innovation Solution
A composite liquid crystal composition is developed, combining liquid crystal compounds with biphenyl and other ring structures, along with polymerizable compounds, to achieve a high birefringence index and photostability while maintaining a low driving voltage, by optimizing the content of compounds like those represented by General Formula (I-a) and (II-a) within specific ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the content of liquid crystal compounds with biphenyl or terphenyl skeletons is increased to maintain high birefringence index, then the birefringence index is improved, but the driving voltage increases
Solution Approach 1:
The patent changes the chemical structure parameters of liquid crystal compounds by introducing compounds with specific dielectric constant anisotropy values and naphthalene ring skeletons, while optimizing their content ratios to achieve both high birefringence and low driving voltage
Solution Approach 2:
The patent creates a composite liquid crystal composition by combining multiple types of liquid crystal compounds (biphenyl skeleton compounds, terphenyl skeleton compounds, and naphthalene ring skeleton compounds) with a polymerizable compound, where each component contributes different properties to achieve overall optimization
2Measurement precision
If the content of liquid crystal compound with naphthalene ring skeleton is increased to increase birefringence index, then the birefringence index is improved, but the photostability of liquid crystal composition decreases
Solution Approach 1:
The patent optimizes the content ratio of naphthalene ring skeleton compounds to be 5-50 wt% of the total liquid crystal compound content, and sets the dielectric constant anisotropy within specific ranges to achieve both high birefringence and photostability
Solution Approach 2:
The patent assigns different functional roles to different compound types: biphenyl and terphenyl compounds provide structural stability and photostability, while naphthalene ring skeleton compounds contribute to high birefringence, creating a balanced composition
3Use of energy by moving object
If the liquid crystal composition is optimized for low driving voltage, then the driving voltage is reduced, but the birefringence index may be insufficient
Solution Approach 1:
The patent sets the dielectric constant anisotropy of the liquid crystal composition to be +3.0 or more, which enables low driving voltage operation while maintaining sufficient birefringence index through the synergistic effect of multiple compound types
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 a birefringence index of 0.16 or more, high photostability, and a driving voltage of 0.9 V/µm or less, suitable for low-voltage operation and battery-driven liquid crystal devices.
Implementation Method 1
a liquid crystal composition which contains a liquid crystal compound and a polymerizable compound
Data Source
AI summary
Provided is a composite liquid crystal composition which contains a liquid crystal compound and a polymerizable compound, has sufficiently high Δn, further has high photostability, and can constitute a liquid crystal device capable of being driven at a low voltage. The composite liquid crystal composition includes, as the liquid crystal compound, a compound having a biphenyl skeleton and two or more compounds represented by Formula (I-a), in which the content of the compound having a biphenyl skeleton is 20% by mass or less of the liquid crystal compounds, and the content of the compound represented by Formula (I-a) in which C1 represents a 1, 4-cyclohexylene group and n1 is not 0 is 45% by mass or more of the liquid crystal compounds; and as the polymerizable compound, one or more compounds selected from the compounds represented by Formulas (II-a1) and (II-a2) and a compound represented by (II-b), in which the total content of the liquid crystal compounds is 65% to 85% by mass, and the total content of the polymerizable compounds is 15% to 35% by mass.