Photoalignment Layer Preparation for Liquid Crystal Displays
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Solution Overview
Problem
Conventional photo-alignment methods for liquid crystal display elements face challenges with low imidization ratios and photosensitivity, particularly with polyamic acids containing a cyclobutane skeleton, which affect the uniformity and stability of liquid crystal alignment.
Innovation Solution
A method involving the preparation of a photo-alignment layer by reacting a diamine with a tetracarboxylic acid or its anhydride, forming a polymer with imide groups, which is then dissolved in an organic solvent, coated, and subjected to sintering and light irradiation, enhancing imidization ratio and photosensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyamic acids with cyclobutane skeleton are used for photo-alignment, then liquid crystal alignment function is achieved, but imidization ratio and photosensitivity are low
Solution Approach 1:
The patent modifies the chemical structure parameters of the polyamic acid by introducing specific substituents (fluoroalkyl groups, alkoxy groups, or alkyl groups) at defined positions (R1-R6) of the cyclobutane skeleton. This structural parameter change enhances both the imidization ratio during sintering and the photosensitivity after imidization, while maintaining the liquid crystal alignment function. The controlled substitution at specific molecular positions optimizes the balance between thermal processing and photo-alignment properties.
2Reliability
If polyamic acids with cyclobutane skeleton are used for photo-alignment, then liquid crystal alignment function is achieved, but photosensitivity is low
Solution Approach 1:
The patent introduces electron-donating or electron-withdrawing substituents (fluoroalkyl, alkoxy, or alkyl groups) at specific positions (R1-R6) of the cyclobutane skeleton to modify the electronic parameters of the polyamic acid molecules. These parameter changes enhance the photosensitivity by improving the photo-induced imidization reaction efficiency and the photo-alignment effect, while maintaining structural integrity for reliable liquid crystal alignment.
3Reliability
If conventional rubbing method is used for liquid crystal alignment, then alignment is achieved, but fine dusts and electrostatic discharge are generated
Solution Approach 1:
The patent replaces the mechanical rubbing process with a photo-alignment method. Instead of physically rubbing the polyamic acid film with fibers (which generates dust and electrostatic discharge), the invention uses light irradiation to induce imidization and alignment of the photo-aligned layer. This substitution eliminates contact-based harmful effects while achieving the same liquid crystal alignment function through photochemical reactions.
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 approach results in a photo-alignment layer with improved imidization ratio, excellent liquid crystal aligning stability, chemical resistance, and reduced luminance variation, effectively addressing the limitations of existing methods.
Implementation Method 1
a sintering process for forming a liquid crystal alignment layer
Implementation Method 2
liquid crystals are aligned using anisotropy induced to the polymer film by light irradiation
Data Source
AI summary
The present invention relates to a method for preparing a photo-alignment layer. The photo-alignment layer prepared by the preparation method exhibits a high imidization ratio as well as an excellent aligning stability of liquid crystal, chemical resistance and strength, and has an excellent afterimage suppressing effect by an AC driving of a liquid crystal display element.