Photo-alignment Layer for Liquid Crystal Display
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Solution Overview
Problem
The rubbing method for aligning liquid crystals in liquid crystal displays generates fine dust and static electricity, leading to manufacturing issues and suboptimal image quality due to non-uniform alignment.
Innovation Solution
A photo-alignment agent comprising polyimide and polyamic acid with a capping group, including specific compounds and crosslinking reaction groups, is used to form a photo-alignment layer that aligns liquid crystals using polarized light, improving film hardness and minimizing afterimage deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the rubbing method is used to align liquid crystals, then the liquid crystal alignment is achieved, but fine dust and static electricity are generated causing manufacturing problems and non-uniform alignment
Solution Approach 1:
The patent replaces the mechanical rubbing method with a photo-alignment method using light irradiation. The polymer film's anisotropy is induced by light rather than mechanical friction, eliminating dust and static electricity generation while achieving uniform liquid crystal alignment through optical field control.
Solution Approach 2:
The patent changes the alignment mechanism from mechanical friction to photo-induced anisotropy. By controlling light irradiation parameters (intensity, wavelength, polarization direction) and polymer film properties (molecular orientation, photo-sensitive groups), uniform alignment is achieved without mechanical contact that generates harmful factors.
2Manufacturing precision
If the rubbing method is used to align liquid crystals, then alignment is achieved, but image quality deteriorates due to non-uniform alignment
Solution Approach 1:
The patent replaces mechanical rubbing with photo-alignment to achieve more uniform liquid crystal orientation. The optical method provides consistent alignment across the entire substrate area, eliminating the non-uniformity that occurs with mechanical rubbing and thereby improving image quality consistency and display reliability.
3Object-generated harmful factors
If a photo-alignment method is used instead of rubbing, then dust and static electricity generation is eliminated, but additional process complexity is introduced
Solution Approach 1:
The patent replaces the simple mechanical rubbing process with a photo-alignment process that requires light irradiation equipment and photo-sensitive polymer materials. While this eliminates dust and static electricity generation, it does introduce additional process complexity through the need for UV irradiation systems and controlled photochemical reaction conditions.
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 solution enhances the uniformity of liquid crystal alignment, improving image quality and reducing afterimage issues while avoiding the drawbacks of the rubbing method, such as dust and static electricity generation.
Implementation Method 1
a photo-alignment method wherein anisotropy is induced in a polymer film by light irradiation
Implementation Method 2
a photo-alignment agent including: at least one of a polyimide and a polyamic acid, and a capping group connected to a main chain end of at least one of the polyimide and the polyamic acid
Data Source
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AI summary
A liquid crystal display including a first substrate, a thin film transistor disposed on the first substrate, a first electrode connected to the thin film transistor, and a first alignment layer disposed on the first electrode, wherein the first alignment layer includes polyimide and a capping group connected to a main chain end of the polyimide, and the capping group contains at least one of a first compound represented by following Chemical Formula 1, and a second compound represented by following Chemical Formula 2: A1 and A2 are, independently of each other, an aromatic compound having 4 to 20 carbon atoms or an aliphatic cyclic compound having 4 to 20 carbon atoms; and B 1 and B2 are, independently of each other, a crosslinking reaction group containing an alkylene group (-CnH2n-, n is a natural number).