Photoalignment Material UV Stabilizer LCD Alignment
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Solution Overview
Problem
The photoalignment process for liquid crystal display (LCD) devices faces challenges such as damage from static electricity, pollution, and reduced voltage holding ratio (VHR) due to side reactions from UV irradiation, which complicates mass production and affects display quality.
Innovation Solution
A photoalignment material comprising a photoalignment polymer, an ultraviolet stabilizer, and an organic solvent, with the ultraviolet stabilizer absorbing or blocking UV light to prevent side reactions, and an epoxy compound with two to four epoxy groups to enhance alignment stability, is used to form a stable alignment layer on a display substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rubbing process is used to form an alignment layer, then liquid crystal alignment can be achieved, but static electricity damages the display substrate and pollution stains the substrate surface
Solution Approach 1:
The patent replaces the mechanical rubbing process with a photoalignment process using UV light irradiation. The photoalignment material contains photoreactive groups that undergo photoisomerization when exposed to UV light, causing liquid crystal molecules to align in the desired direction without mechanical contact, thereby eliminating static electricity generation and substrate pollution from rubbing
Solution Approach 2:
The patent modifies the chemical composition of the alignment layer by incorporating specific photoalignment materials with photoreactive groups (such as cinnamate, coumarin, or azide groups) that change their molecular structure upon UV irradiation. This parameter change enables alignment through optical rather than mechanical means, resolving the harmful effects of the rubbing process
2Ease of operation
If UV light is used to photolyze photoalignment material, then liquid crystal alignment is induced, but side reactions reduce voltage holding ratio and worsen afterimages
Solution Approach 1:
The patent introduces UV stabilizers (such as hindered amine light stabilizers or benzotriazole derivatives) as additives in the photoalignment material. These stabilizers are specifically positioned to absorb UV light at wavelengths that would otherwise cause harmful side reactions, while allowing the photoreactive groups to undergo beneficial photoisomerization. This local quality enhancement protects against UV-induced degradation without compromising alignment functionality
Solution Approach 2:
The patent converts the potentially harmful UV light into a beneficial alignment mechanism. By carefully selecting photoreactive groups and UV stabilizers, the UV irradiation that would normally cause side reactions and degradation is instead harnessed to induce controlled photoisomerization for alignment, while the stabilizers prevent the harmful side reactions
3Ease of manufacture
If photoalignment material is coated on base substrate, then alignment layer is formed, but mass production is difficult due to weak alignment characteristics
Solution Approach 1:
The patent creates a composite photoalignment material system combining multiple components: photoreactive groups (cinnamate, coumarin, azide), UV stabilizers (hindered amine light stabilizers, benzotriazole derivatives), and appropriate solvents. This composite formulation achieves both strong alignment characteristics and manufacturing feasibility by optimizing the interaction between components, enabling reliable mass production while maintaining high alignment 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 solution improves the stability and voltage holding ratio of the alignment layer, reducing afterimages and enhancing the display quality of LCD panels by preventing side reactions and ensuring uniform coating, thus facilitating more reliable and efficient mass production.
Implementation Method 1
The photoalignment additive comprises an ultraviolet stabilizer to block or to absorb ultraviolet light
Implementation Method 2
photolyzing, photoisomerizing, or photopolymerizing the photoalignment material using light
Implementation Method 3
photolyzing, photoisomerizing, or photopolymerizing the photoalignment material using light
Data Source
AI summary
A photoalignment material and a method of manufacturing of a display substrate using the photoalignment material are disclosed. The photoalignment material includes a photoalignment polymer, a photoalignment additive, and an organic solvent. When the photoalignment additive is used, a side reaction due to ultraviolet (UV) light may be prevented, and the stability of alignment layer may be improved.