Acrylate Compound Photo-Alignment Layer
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Solution Overview
Problem
Conventional photoreactive polymers for liquid crystal alignment exhibit poor thermal stability, low solubility in organic solvents, and limited flexibility in changing alignment direction based on polarization direction, which hinders their application in high-definition LCDs and three-dimensional imaging.
Innovation Solution
Development of an acrylate compound with a photoreactive group featuring a bulky substituent, allowing for improved alignment properties, high solubility in organic solvents, and the ability to change alignment direction in response to polarization direction, achieved through a radical polymerization process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional photoreactive polymers (polycinnamate polymers) are used for photo-alignment, then liquid crystal alignment can be achieved through photopolymerization, but the main chain exhibits poor thermal stability
Solution Approach 1:
The invention divides the polymer structure into distinct segments: a stable main chain (polymethyl methacrylate or polyacrylonitrile) and separate photoreactive side chains (cinnamate groups). This segmentation allows the main chain to provide thermal stability while the side chains perform photoreaction, resolving the contradiction between thermal stability and photoreactivity.
Solution Approach 2:
The invention introduces a spacer group as an intermediary between the main chain and the photoreactive cinnamate group. This spacer mediates the interaction, allowing the photoreactive group to perform its function while being isolated from the main chain, thereby preserving the main chain's thermal stability.
2Reliability
If photoreactive polymers with long spacers are added between main chain and photoreactive group to improve photoreactivity, then alignment properties improve, but thermal stability deteriorates
Solution Approach 1:
The invention optimizes the parameters of the spacer group (length, structure) to achieve the right balance. By carefully selecting the spacer parameters and using intramolecular hydrogen bonding, the invention maintains short effective spacing for good alignment while preserving thermal stability through the stable main chain structure.
3Reliability
If photoreactive cyclic-olefin polymer is used to improve alignment properties, then alignment characteristics improve, but solubility to organic solvents decreases
Solution Approach 1:
The invention changes the chemical parameters of the polymer by selecting main chains (polymethyl methacrylate, polyacrylonitrile) and side chain compositions that provide both good solubility in organic solvents and excellent alignment properties through photoreaction.
Solution Approach 2:
The invention creates a composite structure combining a stable main chain with photoreactive side chains, achieving a material that exhibits both good solubility characteristics and superior alignment properties, resolving the contradiction between these two features.
4Reliability
If rubbing process is used for liquid crystal alignment, then alignment can be achieved, but mechanical scratches remain on the surface and static electricity may destroy TFTs
Solution Approach 1:
The invention replaces the mechanical rubbing process with a photo-alignment process using photoreactive polymers. UV irradiation induces photoreaction in the cinnamate groups, creating alignment without mechanical contact, thereby eliminating surface scratches and static electricity generation while achieving the same alignment function.
5Reliability
If conventional photoreactive polymers are used, then photo-alignment can be achieved, but readiness for change in alignment direction based on polarization direction is limited
Solution Approach 1:
The invention creates a dynamic alignment system where the photoreactive cinnamate groups can reorient in response to changes in UV polarization direction. The intramolecular hydrogen bonding and spacer design enable the side chains to rotate and realign, providing adaptability and versatility for changing alignment directions while maintaining stable photo-alignment.
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 acrylate compound and polymer demonstrate enhanced alignment properties, thermal stability, and workability, enabling their use in high-definition LCDs and three-dimensional imaging applications with improved production yield and flexibility.
Implementation Method 1
Photo-alignment refers to the mechanism using a linearly polarized UV radiation to cause the photoreactive groups of a defined photoreactive polymer to participate in a photoreaction, aligning the main chain of the polymer in a defined direction to form a photo-polymerized liquid crystal alignment layer with aligned liquid crystals.
Implementation Method 2
The photo-aligned polymers used in these patent and research papers are mostly polycinnamate polymers, such as poly(vinylcinnamate) (PVCN) or poly(vinyl methoxycinnamate) (PVMC). In the case of photo-alignment of the polymers, the double bond of cinnamate exposed to UV radiation participates in a [2+2] cycloaddition reaction to form cyclobutane, which provides anisotropy to cause liquid crystal molecules aligned in one direction, inducing liquid crystal alignment.
Data Source
AI summary
Disclosed herein are an acrylate compound having a photoreactive group, a photoreactive acrylate polymer, and a photo-alignment layer including the same that not only have excellent alignment properties and alignment rate and readiness for change in the alignment direction based on the polarization direction of radiation, but also exhibit a high solubility to organic solvents and good workability.