Liquid Crystal Aligning Agent Composition for Mild Curing
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Solution Overview
Problem
Conventional liquid crystal alignment methods, such as the rubbing method and photo-alignment using polyimide, face challenges in achieving high imidization rates under mild curing conditions while minimizing side reactions and ensuring stability, particularly in the manufacturing process of liquid crystal display devices.
Innovation Solution
A liquid crystal aligning agent composition comprising a first polymer with specific repeating units, a second polymer, a compound with multiple epoxy groups, and a catalyst, including cyclic and linear tertiary amines, which allows for direct light irradiation without high-temperature heat treatment, enhancing alignment properties and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high temperature heat treatment (300°C or higher) is applied to achieve sufficient imidization of polyamic acid, then imidization rate is improved, but manufacturing complexity and energy consumption increase significantly
Solution Approach 1:
The patent introduces a catalyst (triamine compound) that changes the chemical reaction parameters, enabling polyamic acid imidization to proceed efficiently at lower temperatures (200-230°C) rather than requiring high temperatures (300°C or higher). The catalyst modifies the reaction kinetics, achieving sufficient imidization rates under milder curing conditions.
Solution Approach 2:
The triamine compound acts as an intermediary substance that facilitates the imidization reaction between polyamic acid and water. The catalyst mediates the chemical transformation, enabling the reaction to proceed at lower temperatures while maintaining high imidization rates, thus resolving the contradiction between reliability and manufacturing complexity.
2Reliability
If conventional polyimide is used for photo-alignment, then alignment performance is improved, but solubility deteriorates making direct solution coating difficult
Solution Approach 1:
The patent segments the polyimide molecule into a precursor form (polyamic acid) that possesses both good solubility and the ability to transform into the desired polyimide structure. The polyamic acid can be dissolved in conventional solvents for coating, then transformed in-situ upon contact with moisture and catalyst to form the aligned polyimide structure.
Solution Approach 2:
The patent performs preliminary action by pre-synthesizing polyamic acid with specific molecular structure that ensures both solubility and subsequent transformability. The polyamic acid is prepared in advance with controlled molecular weight and structure to enable easy coating, then transforms in-situ to form the final polyimide alignment layer.
3Ease of manufacture
If polyamic acid is coated and heat treated at 200-230°C to form polyimide, then manufacturing feasibility is improved, but imidization rate deteriorates due to insufficient temperature
Solution Approach 1:
The patent changes the chemical reaction parameters by introducing a catalyst (triamine compound) that enables the imidization reaction to proceed efficiently at lower temperatures. The catalyst modifies the activation energy requirements, allowing sufficient imidization to occur at 200-230°C rather than requiring 300°C or higher.
Solution Approach 2:
The triamine compound serves as an intermediary that facilitates the imidization reaction at lower temperatures. It mediates between the polyamic acid and water, enabling the chemical transformation to proceed with high efficiency under milder curing conditions, thus resolving the contradiction between manufacturing feasibility and imidization rate.
4Reliability
If rubbing method is used for liquid crystal alignment, then alignment capability is improved, but harmful factors (dust and ESD) increase
Solution Approach 1:
The patent replaces the mechanical rubbing system with a chemical-photo system. Instead of using physical contact with rubbing fibers that generate dust and static electricity, the invention uses photo-alignment of polyimide molecules induced by UV irradiation. This substitutes mechanical alignment with optical-chemical alignment, eliminating the harmful effects of rubbing while maintaining alignment capability.
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 a high imidization rate under mild curing conditions, reduces light irradiation energy, and improves the voltage holding ratio and mechanical strength of the liquid crystal alignment film, while maintaining excellent storage stability and alignment properties.
Implementation Method 1
a catalyst comprising at least one selected from the group consisting of a cyclic tertiary amine compound having 1 to 10 hydroxy groups introduced therein, and a linear tertiary amine compound having 2 to 10 hydroxy groups introduced therein
Implementation Method 2
a photo-alignment method of inducing anisotropy in a polymer film by light irradiation rather than the rubbing, and aligning liquid crystals using the anisotropy
Data Source
AI summary
The present invention relates to a liquid crystal aligning agent composition capable of securing a high imidization rate under relatively mild curing conditions, minimizing side reactions and thus having excellent stability, a method for producing a liquid crystal alignment film using the same, and a liquid crystal alignment film and a liquid crystal display device using the same.