Polyimide Alignment Layer Stabilizes Pre-Tilt Angle in LCDs
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Solution Overview
Problem
Twisted-nematic liquid crystal displays experience changes in pre-tilt angle of liquid crystal molecules after driving, leading to luminance differences between black and white modes and the formation of afterimages.
Innovation Solution
An alignment layer formed by copolymerizing a dianhydride monomer and a diamine monomer, specifically using compounds represented by certain formulas, is used between substrates in a liquid crystal display to stabilize the pre-tilt angle, reducing luminance differences between black and white modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If twisted-nematic liquid crystal display is used for high transmittance and fast response speed, then response speed and transmittance are improved, but pre-tilt angle changes after driving causing luminance difference and afterimages
Solution Approach 1:
The invention changes the chemical composition parameters of the alignment layer by using a copolymer of polyamic acid and polyimide with specific structural characteristics. This compositional parameter change stabilizes the pre-tilt angle of liquid crystal molecules, preventing the luminance difference and afterimages that occur in conventional twisted-nematic displays while maintaining fast response speed and high transmittance
Solution Approach 2:
The invention employs a composite alignment layer made from copolymerizing polyamic acid and polyimide components. This composite material structure provides both the stability needed to maintain pre-tilt angle and the performance characteristics for fast response and high transmittance, resolving the contradiction between speed and stability
2Stability of the object's composition
If alignment layer is designed to stabilize pre-tilt angle, then luminance difference and afterimages are reduced, but device structure becomes more complex
Solution Approach 1:
The copolymer alignment layer performs multiple functions simultaneously: it aligns liquid crystal molecules, stabilizes the pre-tilt angle during operation, and maintains fast response characteristics. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity while achieving pre-tilt angle stability
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 alignment layer effectively suppresses changes in the pre-tilt angle, minimizing luminance differences and preventing afterimages by maintaining a stable pre-tilt angle under driving conditions.
Implementation Method 1
an alignment layer formed on the first substrate and the second substrate, including a polymer obtained by copolymerizing a dianhydride monomer and a diamine monomer
Data Source
AI summary
A liquid crystal display includes: a first substrate and an opposing second substrate; an alignment layer formed on the first substrate and the second substrate; and a liquid crystal layer interposed between the first substrate and the second substrate. The alignment layer includes a copolymer including a dianhydride monomer and a diamine monomer.