Polyphosphazene Alignment Layer for Liquid Crystal Displays
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Solution Overview
Problem
The existing alignment layers in liquid crystal display panels face issues with phase separation, smearing, and decreased mechanical strength due to the use of polyimide molecules with bulky functional groups, which affect display quality and lead to afterimages.
Innovation Solution
A composition for an alignment layer comprising a polyphosphazene-based compound with a polyphosphazene backbone, a reactive mesogen element, and a vertical alignment element, along with a solvent of low boiling point, is used to form a single component macromolecule that prevents phase separation and smearing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyimide molecules with bulky functional groups are used, then alignment function is achieved, but phase separation occurs causing smearing
Solution Approach 1:
The patent combines the vertical alignment element and reactive mesogen into a single integrated polyimide molecule structure. This merging eliminates the phase separation issue that occurs when separate functional groups are used, as the alignment function and reactive mesogen remain covalently bonded throughout the polymer chain, ensuring compositional stability while maintaining the vertical alignment function.
Solution Approach 2:
The patent modifies the molecular structure parameters of the polyimide by introducing specific functional groups (cyano groups for vertical alignment and reactive mesogen groups) at controlled positions and concentrations. This parameter optimization prevents phase separation while maintaining the necessary alignment function, resolving the contradiction between reliability and compositional stability.
2Ease of manufacture
If functional groups are combined with diamine, then polyimide formation is achieved, but polymerization time becomes too long and mechanical strength decreases
Solution Approach 1:
The patent segments the polyimide formation process into two stages: first forming the polyimide backbone through diamine and anhydride reaction, then introducing the vertical alignment element and reactive mesogen through subsequent reactions. This segmentation allows the main polymerization to proceed efficiently while the functional groups are added in controlled steps, reducing overall polymerization time and maintaining mechanical strength.
Solution Approach 2:
The patent performs preliminary actions by pre-forming the polyimide backbone with appropriate functional groups before introducing the vertical alignment element and reactive mesogen. This preliminary structure formation enables faster subsequent polymerization and reduces the overall time required while maintaining the mechanical properties of the polyimide.
3Reliability
If reactive mesogen content is increased, then alignment performance improves, but mechanical strength decreases due to decreased reactivity
Solution Approach 1:
The patent applies local quality by concentrating the reactive mesogen and vertical alignment element at specific locations within the polyimide molecule rather than uniformly distributing them. This localized placement optimizes the alignment performance in the critical regions while maintaining the overall mechanical strength of the polyimide structure through proper molecular architecture.
Solution Approach 2:
The patent creates a composite molecular structure where the polyimide backbone is combined with vertical alignment elements and reactive mesogen groups in a specific architectural arrangement. This composite approach allows high content of functional groups to be incorporated while maintaining mechanical strength through the robust polyimide framework and optimized molecular architecture.
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 enhances the alignment of liquid crystal molecules, prevents smears and afterimages, and maintains mechanical strength by using a single component macromolecule and a low-boiling-point solvent to control the thermal reactions, thereby improving display quality.
Implementation Method 1
Liquid crystal molecules of the liquid crystal display panel may be aligned in a uniform direction to have uniform brightness and a high contrast ratio
Implementation Method 2
a composition for an alignment layer includes about 1 percent (%) by weight to about 30% by weight of a polyphosphazene-based compound and a solvent
Data Source
AI summary
A composition for an alignment layer includes about 1% by weight to about 30% by weight of a polyphosphazene-based compound and a remainder of a solvent. The polyphosphazene-based compound includes a polyphosphazene backbone, a reactive mesogen element linked to the polyphosphazene backbone, and a vertical alignment element linked to the polyphosphazene backbone.