Photocrosslinkable Diamine Alignment Layers for MVA Displays
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Solution Overview
Problem
Current methods for producing orientation layers for liquid crystal displays, such as rubbed polyimides, face issues like dust formation, scratches, and complex manufacturing processes, while existing photo-polymerizable alignment materials are not optimized for Multi-Domain Vertical Alignment (MVA) mode requirements, particularly in achieving high voltage holding ratios and stable pre-tilt angles.
Innovation Solution
Development of a diamine compound with specific molecular structures, including carbocyclic or heterocyclic aromatic groups and aliphatic diamine groups, which react with tetracarboxylic acid anhydrides to form polyamic acids or polyimides, enabling the creation of alignment layers with improved optical and electro-optical properties suitable for MVA mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If rubbed polyimide orientation layers are used, then alignment direction can be controlled, but dust formation and scratches occur during rubbing process
Solution Approach 1:
The patent replaces the mechanical rubbing process with a photo-polymerization process. The orientation layer is formed by irradiating a photopolymerizable composition with polarized light, which induces molecular alignment through photochemical reactions rather than mechanical contact. This eliminates dust formation and scratches associated with rubbing while maintaining alignment direction control.
Solution Approach 2:
The patent changes the fundamental parameter of the alignment process from mechanical force (rubbing) to optical energy (photo-polymerization). By using photopolymerizable compounds with specific molecular structures and irradiating with polarized light of specific wavelengths and intensities, the alignment is achieved through photochemical reactions, fundamentally changing the process parameters to eliminate mechanical damage.
2Adaptability or versatility
If protrusions are used for MVA mode, then liquid crystal domains can be switched in different directions, but manufacturing process becomes complex
Solution Approach 1:
The patent extracts the alignment function from the substrate structure (protrusions) and transfers it to the orientation layer material itself. By incorporating photopolymerizable groups with specific spatial arrangements in the molecular structure, the multi-domain alignment capability is built into the material, eliminating the need for complex substrate protrusion structures and their associated manufacturing steps.
Solution Approach 2:
The patent uses composite photopolymerizable compositions containing diamine compounds with specific molecular structures (combining aromatic groups, alicyclic groups, and photopolymerizable groups) that provide both alignment and multi-domain switching capabilities. This composite material approach integrates multiple functions into a single layer, simplifying the overall device structure and manufacturing process.
3Ease of manufacture
If conventional photo-polymerizable alignment materials are used, then manufacturing is simplified, but voltage holding ratio and pre-tilt angle stability are insufficient
Solution Approach 1:
The patent optimizes the molecular parameters of the photopolymerizable compound, specifically incorporating diamine compounds with aromatic groups (for rigidity and thermal stability), alicyclic groups (for structural stability), and photopolymerizable groups (for light-induced alignment). This parameter optimization maintains manufacturing simplicity while significantly improving voltage holding ratio and pre-tilt angle stability.
Solution Approach 2:
The patent develops composite photopolymerizable compositions with specific molecular architectures that combine multiple functional groups in defined ratios and configurations. These composite materials provide both the ease of photopolymerization-based manufacturing and the enhanced electrical and thermal stability required for reliable MVA mode operation.
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 diamine-based alignment layers provide enhanced voltage holding ratios, thermal stability, and controlled pre-tilt angles, simplifying the manufacturing process and improving display performance with wide viewing angles and high brightness.
Implementation Method 1
the reaction of a diamine compound represented by the general formula (I) and optionally of one or more additional other diamines, with one or more tetracarboxylic acid anhydrides
Implementation Method 2
The production procedure for obtaining orientation layers in which the direction of orientation is induced by irradiation with polarized light
Data Source
AI summary
A diamine compound of formula (I) is proposed as well as polymers, copolymers, polyamic acids, polyamic acid esters, or polyimides based on such compound.