PSA Liquid Crystal Composition Stabilizing Pretilt Angles
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Solution Overview
Problem
PSA-type liquid crystal display devices suffer from image sticking and alignment stability issues due to insufficient structural rigidity of polymerizable compounds, leading to changes in pretilt angles and precipitation problems, which affect display quality and response speed.
Innovation Solution
A PSA-type liquid crystal composition comprising a host liquid crystal and a polymerizable component with specific compounds of general formulas I-1, I-2, and I-3, which improve intersolubility and polymerization stability, preventing crystallization and image sticking, and ensuring rapid response speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a polymerizable compound with rigid structure (1,4-phenylene group or biaryl structure) is used to improve structural rigidity and prevent image sticking, then alignment stability is improved, but compatibility with liquid crystal compounds decreases causing precipitation
Solution Approach 1:
The patent introduces flexible alkyl chains at specific positions (R1-R6) of the polymerizable compound molecule. These local flexible segments are incorporated into the otherwise rigid molecular structure to improve compatibility with liquid crystal compounds while maintaining the overall rigidity needed for alignment stability. This resolves the contradiction by making different parts of the molecule serve different functions.
Solution Approach 2:
The patent creates a composite molecular structure combining rigid aromatic rings (for structural rigidity and alignment stability) with flexible alkyl chains (for compatibility and solubility). This composite approach allows the polymerizable compound to simultaneously achieve both alignment stability and compatibility with liquid crystal compositions, preventing precipitation.
2Reliability
If polymerizable compounds with no ring structure (dipentaerythritol pentaacrylate or hexaacrylate) are used, then compatibility with liquid crystal compounds is improved, but structural rigidity becomes insufficient leading to weak alignment control
Solution Approach 1:
The patent places rigid aromatic ring structures at specific positions (R1-R6) within the polymerizable compound molecule, while maintaining flexible alkyl chains in other regions. This local concentration of rigidity provides sufficient structural stiffness for alignment control, while the flexible portions maintain compatibility with liquid crystal compounds.
Solution Approach 2:
The patent combines rigid aromatic ring structures with flexible alkyl chains in a composite molecular architecture. The rigid rings provide the necessary structural rigidity for alignment stability, while the flexible chains ensure compatibility with liquid crystal compositions, resolving the contradiction between rigidity and compatibility.
3Speed
If response speed is improved by using specific liquid crystal compositions, then display performance is enhanced, but pretilt angle stability deteriorates leading to image sticking
Solution Approach 1:
The patent performs preliminary polymerization to form a polymer network structure before the display device is put into service. This pre-formed network provides stable pretilt angle control from the beginning, preventing image sticking while allowing rapid response performance. The alignment is established in advance with the correct pretilt angle.
Solution Approach 2:
The patent carefully controls the polymerization degree and network density as key parameters. By optimizing these parameters, the polymer network provides sufficient structural support for pretilt angle stability while maintaining the liquid crystal's rapid response characteristics. The parameter optimization resolves the contradiction between speed and stability.
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 stable pretilt angles, prevents crystallization, and reduces display defects like image sticking, while maintaining high response speed and compatibility with liquid crystal compounds.
Implementation Method 1
the alignment of liquid crystal molecules is controlled by a polymer network formed by the polymerization of polymerizable compounds
Implementation Method 2
a host liquid crystal A comprising one or more liquid crystal compounds
Data Source
AI summary
A PSA-type liquid crystal composition includes a host liquid crystal A and a polymerizable component B, where the host liquid crystal A includes one or more liquid crystal compounds, and the polymerizable component B includes at least one compound selected from compounds of general formula I-1, general formula I-2 and general formula I-3. A liquid crystal display device includes the PSA-type liquid crystal composition above. The PSA-type liquid crystal composition has better intersolubility, cannot be crystallized at a low-temperature environment, can form a relatively stable pretilt angle after the polymerization of the polymerizable component, avoids the image sticking, and inhibits the occurrence of a display defect, such as Zara Particle, during the polymerization.