Polyimide Vertical Alignment Layer for Liquid Crystal Displays
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Solution Overview
Problem
Conventional liquid crystal displays face challenges in achieving stable alignment of liquid crystal molecules, leading to issues such as drip spots and reduced reliability due to inadequate alignment layers, especially when exposed to heat or UV light.
Innovation Solution
A vertical alignment layer comprising a polyimide derived from a composition including a dianhydride-based compound and a specific compound represented by Chemical Formula 1, which enhances the rigidity, hydrophobicity, and alignment stability of liquid crystal molecules, with an imidization ratio greater than 70% to improve the reliability and reduce printing faults.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional alignment layer is used, then the liquid crystal molecules can be aligned, but the alignment stability deteriorates when exposed to heat or UV light, leading to drip spots and reduced reliability
Solution Approach 1:
The patent modifies the chemical structure of the polyimide alignment layer by introducing specific side chain groups (cyano, fluorine, or chlorine-containing groups) to change the material's resistance parameters against heat and UV degradation, thereby maintaining alignment stability under harsh conditions
Solution Approach 2:
The invention creates a composite alignment layer by combining polyimide with specific side chain compounds having distinct functional groups (cyano, fluorine, chlorine), where each component contributes different properties: polyimide provides structural framework while the side chains provide thermal and UV stability
2Ease of manufacture
If the alignment layer structure is simplified, then the manufacturing process becomes easier, but the alignment precision and uniformity deteriorate, leading to printing faults
Solution Approach 1:
The patent optimizes the imidization ratio parameter to be greater than 70%, which balances the crosslinking density to achieve both good alignment uniformity and ease of manufacturing through standard spin-coating processes
3Reliability
If the polyimide crosslinking is increased to improve alignment stability, then the resistance to heat and UV improves, but the ion density increases, affecting display quality
Solution Approach 1:
The patent carefully controls the imidization ratio parameter within a specific range (greater than 70%) to optimize the crosslinking density, achieving sufficient thermal and UV resistance while limiting ion generation through moderate crosslinking rather than excessive crosslinking
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 proposed solution effectively reduces drip spots and improves the reliability of the alignment layer, maintaining high voltage holding rates and low ion density even under heat or UV exposure, thereby enhancing the overall performance and stability of the liquid crystal display.
Implementation Method 1
An alignment layer may be formed on the inner surfaces of the two display panels to align liquid crystal molecules of the liquid crystal layer
Implementation Method 2
voltages are applied to the field generating electrodes so as to generate an electric field in the liquid crystal layer, and the alignment of liquid crystal molecules of the liquid crystal layer is determined by the electric field
Data Source
AI summary
An alignment layer according to an exemplary embodiment of the present invention includes a polyimide, wherein the polyimide is derived from a composition including a dianhydride-based compound, and a compound represented by a Chemical Formula 1:wherein, in the above Chemical Formula 1, X1 and X2 are independently F, Cl, or CN, and R1 is a substituted or non-substituted C1-C12 alkyl group, a substituted or non-substituted C1-C12 alkoxy group, a substituted or non-substituted C1-C12 halogen-containing alkyl group, a substituted or non-substituted C1-C12 halogen-containing alkoxy group, or a combination thereof.