LC Alignment Film Using Dendron Diamine for Pretilt Control
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Solution Overview
Problem
Conventional LC alignment films face challenges in achieving high-quality displays with excellent electrooptical properties, stability, and high reliability, particularly in large-area LCD fabrication, due to issues with transparency, solubility, and electrooptical characteristics, as well as limitations in controlling pretilt angles and voltage holding ratios.
Innovation Solution
A composition for an LC alignment film using a diamine compound with dendron side chains, which is copolymerized with aliphatic and aromatic cyclic acid dianhydrides to produce polyamic acid, allowing for improved alignment, chemical resistance, and adjustable pretilt angles, and is applied to form films suitable for twisted nematic or vertical alignment modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional aromatic diamine and aromatic acid dianhydride are used to form polyimide, then thermal stability and mechanical properties are improved, but transparency and solubility deteriorate due to charge transfer complex formation
Solution Approach 1:
The patent introduces dendron side chains with specific functional groups (carboxyl, hydroxyl, or amine groups) at localized positions on the diamine molecule. These localized functional groups disrupt the charge transfer complex formation between aromatic rings while maintaining the overall polyimide structure's thermal stability, thereby improving transparency without sacrificing reliability
Solution Approach 2:
The patent creates a composite molecular structure combining conventional aromatic diamine core with dendron side chains containing aliphatic or aromatic rings with functional groups. This composite structure leverages the thermal stability of aromatic polyimide while the dendron side chains prevent excessive charge transfer complex formation, achieving both high transparency and thermal stability
2Manufacturing precision
If conventional polyimide is used for alignment film, then excellent alignment is achieved, but control over pretilt angle is limited and voltage holding ratio is insufficient
Solution Approach 1:
The patent systematically varies the dendron side chain structure (aliphatic vs. aromatic rings, different functional groups, varying chain lengths) to precisely control the pretilt angle. By changing these molecular parameters, the patent achieves可调 pretilt angles from 0-30 degrees while maintaining excellent alignment uniformity through the systematic modification of side chain characteristics
Solution Approach 2:
The patent creates a dynamic system where the pretilt angle can be adjusted by modifying the dendron side chain composition. The flexible side chains allow the polymer to adapt its conformation in response to different liquid crystal molecules and processing conditions, enabling versatile pretilt angle control while maintaining stable alignment
3Stability of the object's composition
If functional diamine with side chains is used to increase pretilt angle, then stability is improved, but transparency and electrooptical characteristics worsen
Solution Approach 1:
The patent strategically places functional groups (carboxyl, hydroxyl, amine) at specific locations on the dendron side chains, creating localized polar regions that stabilize pretilt angle through controlled interactions with liquid crystal molecules. These localized functional groups provide stability without extensive charge transfer complex formation that would reduce transparency
Solution Approach 2:
The patent optimizes the parameters of dendron side chains including the type of terminal functional group, the number of dendron units, and the spacing between side chains. By carefully adjusting these parameters, the patent achieves stable pretilt angle control while minimizing the concentration of chromophoric groups that would absorb visible light and reduce transparency
4Manufacturing precision
If conventional rubbing process is used for alignment, then alignment is achieved, but productivity is reduced due to complex process steps and large area fabrication challenges
Solution Approach 1:
The patent extracts the alignment function from the mechanical rubbing process by incorporating alignment-directing dendron side chains directly into the polymer structure. The dendron side chains with functional groups provide intrinsic alignment capability through molecular interactions with liquid crystals, eliminating the need for separate rubbing steps and improving productivity for large-area fabrication
Solution Approach 2:
The patent enables the alignment film to self-align liquid crystals through the inherent properties of dendron side chains. The functional groups on dendron side chains automatically interact with liquid crystal molecules during film formation and curing, providing self-aligned structures without requiring external mechanical intervention, thereby simplifying the process and improving productivity
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 LC alignment film exhibits excellent alignment stability, high light penetration, and controlled pretilt angles, along with enhanced electrooptical properties and printability, enabling high-quality LCD performance with reduced defects and improved reliability.
Implementation Method 1
copolymerized with aliphatic and aromatic cyclic acid dianhydrides to produce polyamic acid
Implementation Method 2
achieve the uniform arrangement of liquid crystal molecules, that is, alignment
Implementation Method 3
followed by imidization
Data Source
AI summary
Disclosed herein is an LC aligning agent using diamine having dendron side chains. In detail, the present invention relates to a composition for an LC alignment film which employs diamine having dendron side chains to produce polyamic acid, followed by imidization. When the LC alignment film is applied to a liquid crystal display device, high heat resistance, high penetration in a visible ray range, excellent alignment, and a high voltage holding ratio are assured. Even though it contains a small amount of functional diamine, a high pretilt angle can be assured. Thus, the pretilt angle is easily controlled and a vertical aligning force is improved.