Liquid Crystal Aligning Agent Epoxy Cross-linker Defect Reduction
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Solution Overview
Problem
Liquid crystal display devices, particularly in the vertical alignment mode, face challenges with defects such as spots and afterimages due to the alignment of liquid crystal molecules, which affect the viewing angle and contrast ratio, and existing solutions do not adequately address these issues.
Innovation Solution
A liquid crystal display device is developed with alignment layers containing a polymer and an epoxy cross-linker, where the polymer includes polyamic acid or polyimide and a compound with an epoxy cross-linker, along with a diamine compound, to improve the alignment and reduce defects like oblique line spots and afterimages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional alignment layers are used to align liquid crystal molecules, then the liquid crystal display device can be manufactured, but defects such as spots and afterimages occur, reducing display quality
Solution Approach 1:
The patent changes the chemical composition parameters of the alignment layer by incorporating specific epoxy cross-linkers with defined molecular structures (Formula 1) and controlling their content (0.1-10 wt%), along with specific diamine compounds (Formula 2) at controlled ratios. These parameter changes in the polymer composition modify the alignment layer's properties to eliminate defects while maintaining proper liquid crystal alignment
Solution Approach 2:
The patent creates a composite alignment layer material combining polyimide or polyamic acid polymers with epoxy cross-linker compounds and diamine compounds. This composite structure integrates multiple functional components: the polymer provides the base alignment properties, while the epoxy cross-linker and diamine compound work together to eliminate defects and improve display quality without causing spots or afterimages
2Reliability
If the alignment layer composition is modified to reduce defects, then display quality improves, but the manufacturing process complexity increases
Solution Approach 1:
The patent merges multiple functional components into a single integrated alignment layer formulation: the polymer (polyimide or polyamic acid), epoxy cross-linker, and diamine compound are combined into one coating solution that is applied in a single step. This merging approach achieves defect reduction without proportionally increasing manufacturing complexity, as all components are incorporated together rather than requiring separate processing steps
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 use of these alignment layers decreases defects and enhances the quality of the liquid crystal display by improving the alignment of liquid crystal molecules, resulting in better viewing angles and contrast ratios, as demonstrated by increased hardness and density of the alignment layer and stable pretilt angles.
Implementation Method 1
a compound including an epoxy cross-linker represented by following Chemical Formula 1
Implementation Method 2
the presence of an alignment layer on the substrate functions to align the liquid crystal molecules at the pretilt angle
Data Source
AI summary
A liquid crystal display device includes a first substrate, a first alignment layer on the first substrate, a second substrate facing the first substrate, a second alignment layer on the second substrate, and a liquid crystal layer between the first substrate and the second substrate and including liquid crystal molecules. The first alignment layer and the second alignment layer include a polymer including at least of polyamic acid, polyimide, and a combination including at least one of the foregoing polymers, and a compound including an epoxy cross-linker represented by Chemical Formula 1.