Liquid Crystal Photoalignment Agent Without Photoinitiators
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Solution Overview
Problem
Existing liquid crystal displays require photoinitiators for polymerization of methacrylate groups, which can lead to incomplete reaction, residual photoinitiator decomposition causing ion adsorption loss and color stains, complicating uniform display quality.
Innovation Solution
A liquid crystal photoalignment agent comprising a copolymer of diamine and dianhydride and a compound of Formula 1, where the compound is hydrophobic and forms islands on a hydrophilic base structure, enabling polymerization of methacrylate groups without a photoinitiator, preventing color stains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If photoinitiators are used for polymerization of methacrylate groups, then polymerization can be initiated, but incomplete reaction occurs and residual photoinitiator decomposes causing ion adsorption loss and color stains
Solution Approach 1:
The patent removes photoinitiators from the liquid crystal composition entirely, replacing them with a photopolymerizable compound containing methacrylate groups that can undergo direct photopolymerization upon UV irradiation. This extraction of the harmful photoinitiator component eliminates the source of color stains and ion adsorption loss while maintaining the ability to form protrusions for liquid crystal alignment.
Solution Approach 2:
The photopolymerizable compound serves dual functions: it acts as both the polymerization substrate and the alignment-forming agent. Upon UV irradiation, the methacrylate groups polymerize directly to form protrusions that align liquid crystal molecules, eliminating the need for separate photoinitiator chemicals and achieving complete reaction without harmful residues.
2Ease of operation
If photoinitiators are used for alignment, then liquid crystal molecules can be aligned with pretilt, but uniform display quality deteriorates due to photoinitiator decomposition
Solution Approach 1:
By removing photoinitiators from the system and using direct photopolymerization of methacrylate-containing compounds, the patent eliminates the decomposition byproducts that cause non-uniform display quality. The alignment process remains effective through protrusion formation, but without the harmful side effects of photoinitiator breakdown.
3Reliability
If complex photoalignment agents are used, then polymerization can occur, but device complexity increases
Solution Approach 1:
The liquid crystal composition uses a multifunctional approach where the same compound serves multiple purposes: it provides the liquid crystal matrix, contains methacrylate groups for photopolymerization, and forms protrusions for alignment. This multi-functionality reduces the need for separate photoinitiator components and simplifies the overall system while maintaining reliable polymerization and alignment functions.
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 solution allows for uniform photopolymerization and formation of protrusions without photoinitiators, maintaining alignment and preventing color stains, thereby enhancing display quality and operational stability.
Implementation Method 1
exposing a prepolymer to ultraviolet light at a desired voltage to polymerize the prepolymer
Implementation Method 2
The copolymer of diamine and dianhydride may be hydrophilic
Implementation Method 3
the compound of Formula 1 may be hydrophobic
Implementation Method 4
The copolymer of diamine and dianhydride may not be miscible with the compound of Formula 1
Data Source
AI summary
A liquid crystal photoalignment agent includes: a copolymer of diamine and dianhydride; and a compound Formula 1 below, wherein an amount of the compound of Formula 1 is less than about 10 weight %, based on a total weight of the liquid crystal photoalignment agent:R1 is a substituted or unsubstituted tetravalent organic group derived from an acid dianhydride, wherein the acid dianhydride is at least one of an aliphatic cyclic acid dianhydride or an aromatic acid dianhydride, R2 is a substituted or unsubstituted trivalent organic group derived from an aromatic diamine, at least one of R1 and R2 is substituted with CF3 or a silyl group, R3 is a residue of a compound including a substituted or unsubstituted aromatic group with a carbon number that is equal to or greater than 6, n is 1 to 5, and * represents a point of attachment.