Polymerizable Polar Compound for Liquid Crystal Alignment
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Solution Overview
Problem
Current liquid crystal display elements face challenges in achieving high chemical stability, efficient alignment of liquid crystal molecules, and long-term voltage holding ratios, particularly in extreme temperatures and under exposure to ultraviolet radiation, while maintaining low viscosity and high optical anisotropy.
Innovation Solution
A polymerizable polar compound with a perfluoroalkyl chain and acryloyloxy group is introduced, which aligns liquid crystal molecules and forms a polymer network upon UV exposure, enhancing stability and alignment properties when used in liquid crystal compositions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional liquid crystal compositions are used, then the elements can operate at standard temperatures, but the elements fail to maintain stable performance in extreme temperatures and under UV exposure
Solution Approach 1:
The patent employs a composite liquid crystal composition containing multiple components: a nematic liquid crystal compound as the base, a polymerizable compound with specific molecular structure (Formula 1) providing UV stability and alignment, and a chiral compound for twist control. This composite approach allows the composition to simultaneously achieve chemical stability, wide temperature range (−40°C to 85°C), and UV resistance that individual components cannot provide alone.
Solution Approach 2:
The patent modifies the molecular structure of the polymerizable compound by varying parameters in Formula (1), including different alkyl chain lengths (R1 with 1-15 carbon atoms), different spacer groups (Sp1 with 1-15 carbon atoms), and different terminal groups (M1 and M2). These parameter changes optimize the balance between stability, solubility, and alignment properties to achieve reliable performance across extreme temperature ranges.
2Reliability
If the liquid crystal composition has high viscosity, then the material is more stable, but the response time of the display element increases
Solution Approach 1:
The patent carefully selects and adjusts the molecular structure parameters of the liquid crystal compounds, including the chain length and branching of alkyl groups, the type of spacer groups, and the core molecular structure. These parameter changes enable the composition to achieve optimal viscosity within the range of 5-500 mPa·s at 20°C, balancing stability with fast response times suitable for dynamic display applications.
3Manufacturing precision
If the liquid crystal composition has high optical anisotropy, then the contrast ratio improves, but the threshold voltage increases leading to higher power consumption
Solution Approach 1:
The patent optimizes the dielectric anisotropy parameter (Δε) of the liquid crystal composition by adjusting the molecular structures and ratios of the components. The composition achieves Δε within the range of -10 to +10, which when combined with optimized cell gap and alignment layer parameters, delivers high contrast ratios while maintaining threshold voltages in the range of 1-10 V, balancing optical performance with acceptable power consumption.
4Reliability
If a polymer network is formed in the liquid crystal composition, then the alignment stability and UV resistance improve, but the solubility of the compound in the composition decreases
Solution Approach 1:
The patent designs the polymerizable compound with specific structural parameters in Formula (1), including controllable molecular weight, flexible spacer groups (Sp1 with 1-15 carbon atoms), and adjustable terminal groups (M1 and M2). These parameter changes ensure sufficient solubility of the polymerizable compound in the liquid crystal composition before polymerization, while enabling formation of a stable polymer network upon UV exposure that provides long-term alignment stability and UV resistance.
5Reliability
If the liquid crystal composition is highly purified, then the chemical stability improves, but the manufacturing complexity and cost increase
Solution Approach 1:
The patent selects liquid crystal compounds and additives with inherently high chemical stability through careful molecular structure design, including the use of fluorinated groups, aromatic cores with stable bonding, and controlled purity specifications. This approach achieves sufficient chemical stability for reliable display operation without requiring excessively complex and costly purification processes, balancing performance with manufacturing feasibility.
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 compound improves the chemical stability, solubility, and voltage holding ratio of liquid crystal display elements, enabling wider temperature ranges, shorter response times, and reduced image burn, while maintaining low viscosity and high optical anisotropy.
Implementation Method 1
a polymerizable polar compound with a perfluoroalkyl chain and acryloyloxy group is introduced, which aligns liquid crystal molecules and forms a polymer network upon UV exposure
Data Source
AI summary
To provide a polar compound having high chemical stability, a high ability to align liquid crystal molecules, and high solubility in a liquid crystal composition, and a high voltage holding ratio of a liquid crystal display element.A compound represented by Formula (1):R1 is a hydrogen atom or an alkyl group that may be substituted; a is 2 to 12; and R2 is Formula (1-a), Formula (1-b), and Formula (1-c);Sp1 to Sp3 are a single bond or an alkylene group that may be substituted; M1 and M2 are H, F, Cl, or an alkyl group that may be substituted; and X1 is —OH, —NH2, —OR3, —N(R3)2, —COOH, —SH or —Si(R3)3.