Liquid Crystal Alignment Film via Composite Photo-Alignment
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Solution Overview
Problem
Conventional liquid crystal alignment methods, such as the rubbing method and photo-alignment using polyimide, face challenges including high energy requirements for alignment, additional heat treatment processes, and limitations in achieving a high voltage holding ratio, which hinder productivity and stability in liquid crystal display devices.
Innovation Solution
A liquid crystal alignment composition comprising a polymer with specific repeating units and a compound having two or more epoxy groups, allowing for direct light irradiation without high-temperature heat treatment, followed by a single heat treatment step to enhance alignment properties and stability, and improve the voltage holding ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyimide is used for photo-alignment method, then liquid crystal alignment property is improved, but light irradiation energy requirement increases and additional heat treatment process is needed
Solution Approach 1:
The invention uses a composite material system consisting of polyamic acid (precursor) combined with photo-alignment agents (such as polyphenyl cyclophane derivatives or polyfluorene derivatives). This composite approach allows the polyamic acid to form polyimide structure that provides good liquid crystal alignment properties while the photo-alignment agents enable effective alignment with reduced light irradiation energy compared to pure polyimide systems.
2Reliability
If polyimide is used for photo-alignment method, then liquid crystal alignment property is improved, but process complexity increases due to additional heat treatment
Solution Approach 1:
The invention performs preliminary photo-alignment treatment on the polyamic acid film before the final heat treatment step. The photo-alignment agents are incorporated into the polyamic acid structure, allowing alignment to be established during the coating and drying stages. The subsequent heat treatment then cures the film without requiring additional alignment steps, thereby reducing overall process complexity.
3Stability of the object's composition
If conventional polyimide is used, then alignment stability is achieved, but voltage holding ratio is insufficient
Solution Approach 1:
The invention creates a composite system where polyamic acid is combined with photo-alignment agents that have specific molecular structures (polyphenyl cyclophane derivatives or polyfluorene derivatives). This composite structure provides both alignment stability through the polyimide formation and improved voltage holding ratio through the photo-alignment agents' contribution to the film's dielectric properties and molecular orientation.
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
This approach reduces light irradiation energy, simplifies the process, and achieves a liquid crystal alignment film with enhanced alignment properties, stability, and high voltage holding ratio, suitable for practical mass production.
Implementation Method 1
irradiating the coating film with light to perform alignment treatment
Implementation Method 2
a compound having two or more epoxy groups in a molecule
Data Source
AI summary
The present invention relates to a liquid crystal alignment composition for the preparation of a liquid crystal alignment film having enhanced alignment property and stability and exhibiting a high voltage holding ratio, a method for preparing a liquid crystal alignment film using the same, and a liquid crystal alignment film and a liquid crystal display device using the same.