Cross-linking Agent for Liquid Crystal Alignment Film
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Solution Overview
Problem
Existing liquid crystal alignment materials face challenges in achieving uniform alignment, high film strength, and reliable electrical properties due to low solubility and dispersibility of cross-linking agents, which affects the performance of liquid crystal displays, especially in low-power applications.
Innovation Solution
A cross-linking agent compound with enhanced solubility and cross-linking effect is introduced, represented by a specific chemical formula, which forms a cyclic structure with a divalent functional group containing a Group 14 element, allowing for improved dispersibility and cross-linking at higher temperatures, and is incorporated into a liquid crystal alignment composition with polyamic acid, polyamic acid ester, or polyimide units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If cross-linking agents are added to liquid crystal alignment composition to improve film strength, then film strength is improved, but solubility and dispersibility decrease leading to non-uniform composition
Solution Approach 1:
The patent modifies the chemical structure of cross-linking agents by introducing specific functional groups and molecular weight ranges to optimize both solubility and cross-linking performance. The cross-linking agents are designed with specific chemical formulas (Formula 1 and Formula 2) that balance polarity and molecular size to achieve uniform dispersion while maintaining film strength.
Solution Approach 2:
The patent creates a composite liquid crystal alignment composition containing multiple components including polyimide or polyamic acid (5-50 wt%), cross-linking agents (1-20 wt% of each Formula 1 and Formula 2), and solvents. This composite approach allows synergistic effects where each component contributes specific properties: polyimide provides alignment functionality, cross-linking agents provide film strength, and solvents ensure uniform dispersion.
2Strength
If simple addition of cross-linking agent compound is used to prepare liquid crystal alignment film, then film strength is improved, but electrical properties at high temperature and low frequency decrease
Solution Approach 1:
The patent introduces different types of cross-linking agents (Formula 1 and Formula 2) with distinct chemical structures to perform specialized functions. Formula 1 cross-linking agents primarily enhance film strength through cross-linking reactions, while Formula 2 cross-linking agents are specifically designed to maintain electrical properties at high temperatures. This local quality differentiation allows simultaneous optimization of mechanical and electrical properties.
3Manufacturing precision
If polyimide is used as liquid crystal alignment material, then alignment property is good, but solubility in solvent is low making solution coating difficult
Solution Approach 1:
The patent uses polyamic acid or polyamic acid ester as precursors before final polyimide formation. These precursor materials possess excellent solubility in common solvents, enabling solution coating processes. The polyamic acid precursors are first applied in solution state, then undergo heat treatment to form the final polyimide alignment layer. This preliminary action allows solution processing while maintaining the desired alignment properties.
Solution Approach 2:
The patent changes the chemical state of the alignment material from fully imidized polyimide to partially imidized polyamic acid or polyamic acid ester intermediates. This parameter change in the degree of imidization dramatically improves solubility while retaining the essential alignment functionality. The chemical structure is optimized to balance solubility and alignment performance.
4Object-affected harmful factors
If light irradiation is used to induce anisotropy in polymer film for photo-alignment, then rubbing method problems are solved, but large panel friction causes haze and white dots
Solution Approach 1:
The patent introduces cross-linking agents as intermediary substances that mediate between the light irradiation process and the polymer film structure. These cross-linking agents facilitate controlled cross-linking reactions during photo-alignment, creating a more robust network that resists the formation of haze and white dots even in large panels. The cross-linking agents act as structural mediators that enhance film integrity during the alignment process.
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 enables the production of liquid crystal alignment films with improved alignment properties, electrical properties, and film strength, while maintaining uniformity and reliability, even at high temperatures, thus enhancing the performance of liquid crystal displays.
Implementation Method 1
a cross-linking agent compound having excellent solubility and improved cross-linking effect
Implementation Method 2
a photo-alignment method is being recently studied, wherein anisotropy is induced to a polymer film by light irradiation instead of friction, and liquid crystals are arranged using the anisotropy
Data Source
AI summary
The present invention relates to a cross-linking agent compound of which end functional group is substituted with a protection group of a specific structure, a liquid crystal alignment composition comprising the cross-linking agent compound and polymer containing repeat units of polyimide or a precursor thereof, a method of preparing liquid crystal alignment film, a liquid crystal alignment film, and a liquid crystal display using the same.