Vertical Aligning Material for LCD via Photoalignment
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Solution Overview
Problem
Current liquid crystal display (LCD) technologies face issues with alignment film materials, such as rubbing alignment materials causing defects and photoalignment materials having poor heat resistance and anchoring abilities, leading to increased manufacturing costs and environmental concerns.
Innovation Solution
A self-aligning material with a polar anchoring group, polymerizable group, intermediate rigid group, and terminal flexible group is developed, which forms a dense polymeric film upon UV exposure, enabling vertical alignment of liquid crystals without the need for a polyimide film, thereby reducing manufacturing costs and improving panel quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If rubbing alignment material is used, then liquid crystal alignment is achieved, but dust particles, electrostatic residual, and brush marks occur leading to decreased product qualified rate
Solution Approach 1:
The patent replaces the mechanical rubbing alignment method with a photoalignment mechanism. Instead of using physical brushes to align liquid crystal molecules, the invention uses UV irradiation to activate photoalignment groups in the polymer material, which then optically induce vertical alignment of liquid crystal molecules. This substitution eliminates mechanical contact that causes dust, electrostatic residue, and brush marks.
Solution Approach 2:
The patent changes the alignment mechanism from mechanical force to optical field interaction. By introducing photoalignment groups that respond to UV light, the material transitions from requiring physical rubbing to achieving alignment through photopolymerization and optical field effects, fundamentally changing the alignment parameter from mechanical stress to optical induction.
2Reliability
If photoalignment PI material is used, then rubbing-related defects are avoided, but heat resistance and aging resistance are poor and anchoring ability is weak
Solution Approach 1:
The patent creates a composite material system combining polymerizable groups, polar anchoring groups, and rigid intermediate groups. This composite structure integrates the advantages of photoalignment (defect-free surface) with enhanced stability through the rigid intermediate groups that provide thermal and aging resistance, and the polar anchoring groups that strengthen liquid crystal anchoring ability.
Solution Approach 2:
The patent assigns different functional groups to different parts of the molecular structure: polymerizable groups for photoalignment function, polar anchoring groups for strong LC anchoring, and rigid intermediate groups for thermal stability. Each local region of the molecule performs a specific function, combining multiple properties in a single material system.
3Manufacturing precision
If PI material is used, then alignment function is provided, but high polarity and water-absorbing capacity cause property changes during storage and transportation
Solution Approach 1:
The patent uses a polymerizable material that forms a crosslinked network structure upon UV irradiation. This creates a stable, low-polarity final product that is resistant to property changes during storage and transportation, replacing the inherently unstable high-polarity PI material.
4Manufacturing precision
If PI film is used, then liquid crystal alignment is achieved, but manufacturing cost increases due to expensive material and complicated film forming procedure
Solution Approach 1:
The patent extracts and eliminates the expensive PI material and its complicated film forming procedures from the manufacturing process. By using a polymerizable material that can be applied as a simple coating and cured by UV light, the invention removes the need for complex PI film formation steps and reduces material costs.
5Manufacturing precision
If PI solution is used, then alignment film is formed, but large amount of NMP solvent requires high energy consumption and harms environment and health
Solution Approach 1:
The patent changes the solvent system from NMP-based to UV-curable polymerizable solvents. This parameter change eliminates the need for high-energy drying processes and removes the environmental and health hazards associated with NMP, while still achieving effective alignment film formation through photopolymerization.
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 material effectively aligns liquid crystals vertically, reducing manufacturing costs and environmental impact by eliminating the need for a polyimide film, while maintaining the reliability and quality of the LCD panel.
Implementation Method 1
The polymerizable group is mainly a dense polymeric film layer formed by polymerization under an action of ultraviolet (UV) light
Implementation Method 2
A main role of the anchoring group is to anchor the material on a surface of a non-polar substrate with a polar group thereof by a physical manner
Data Source
AI summary
Disclosed is a material for a vertical aligning agent, and a molecular structure of the material is shown in formula (I):R-L1P-L2nQ (I)wherein Q is a polar anchor group, L1 is a rigid group, P is a polymerizable group, L2 is a linking group, R is a terminal flexible group, and n is in a range from 1 to 3. In the material, the polar anchor group is connected to the polymerizable group, which is beneficial to increase an aspect ratio of the material. Therefore, a fluid viscosity of the material can be reduced, and a diffusion effect of the material on a substrate can be improved.