Liquid Crystal Alignment Agent Viscosity Control
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Solution Overview
Problem
Existing liquid crystal display devices face issues with pretilt angle stability and uniformity, leading to defects such as mura, and process instability, which result in a high defective rate, despite improvements in response speed and voltage holding ratio.
Innovation Solution
A liquid crystal alignment agent is developed, comprising a polyamic acid dispersion and a polyimide dispersion with specific viscosity ratios, applied to form a liquid crystal alignment film that provides improved alignment properties and stability, ensuring a pretilt angle uniformity of less than 20%.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional liquid crystal alignment agents are used, then response speed and voltage holding ratio are improved, but pretilt angle uniformity deteriorates leading to mura defects
Solution Approach 1:
The patent changes the chemical composition parameters of the alignment agent by incorporating specific compounds (polyamic acid with imidization groups, polyimide with splayed structures, and chiral agents) to achieve both high response speed and uniform pretilt angle, resolving the contradiction between speed improvement and uniformity deterioration
Solution Approach 2:
The patent uses a composite alignment agent formulation combining multiple components (polyamic acid, polyimide, chiral agents, and specific additives) to simultaneously achieve improved response speed and maintained pretilt angle uniformity, preventing mura defects while enhancing display performance
2Reliability
If conventional liquid crystal alignment agents are used, then voltage holding ratio is improved, but process stability deteriorates resulting in high defective rate
Solution Approach 1:
The patent optimizes the molecular weight, viscosity, and chemical structure parameters of the alignment agent components to achieve a balance between high voltage holding ratio and excellent process stability, reducing the defective rate while maintaining reliable electrical performance
Solution Approach 2:
The patent develops an alignment agent formulation that is cost-effective and easy to process, replacing complex and unstable conventional formulations with simpler, more stable compounds that maintain high voltage holding ratio while improving manufacturing yield
3Speed
If high pretilt angle alignment films are used, then response speed and reliability are enhanced, but pretilt angle stability deteriorates causing mura appearance
Solution Approach 1:
The patent incorporates chiral agents and specific molecular structures that provide feedback mechanisms to maintain consistent pretilt angle orientation throughout the liquid crystal layer, ensuring uniformity while achieving high response speed and reliability
Solution Approach 2:
The patent uses locally optimized molecular structures and additives in the alignment agent that specifically target the pretilt angle formation at the alignment film interface, ensuring stable and uniform pretilt angles while maintaining high response performance
Data Source
AI summary
A liquid crystal alignment agent includes a polyamic acid dispersion and a polyimide dispersion. Viscosity of the polyamic acid dispersion and viscosity of the polyimide dispersion satisfy the following relationship:VA-2−VA-1≧4 cpswhereinVA-2 is viscosity of the polyimide dispersion measured at a solid content of 6 wt % at a temperature of 25° C., andVA-1 is viscosity of the polyamic acid dispersion measured at a solid content of 6 wt % at a temperature of 25° C.A liquid crystal alignment film formed from the liquid crystal alignment agent and a liquid crystal display element including the liquid crystal alignment film are also disclosed.