Polyimide Photo-Alignment Layer for TFT-LCD Displays
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Solution Overview
Problem
Current photo-alignment methods for liquid crystal alignment layers in TFT-LCD displays face issues such as low anchoring energy, poor stability, and limitations in industrialization due to high ring strain, photo-thermal instability, and poor stability of the diazo functional group.
Innovation Solution
A polyimide with a graft group bonded to specific side-chain groups, which transforms from a trans to a cis structure under light irradiation, enhancing stability and anchoring force without main chain bond breakage, using commercially available selenide and diazo functional groups.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a photo-alignment method is used to avoid contact and reduce dust, then cleanliness and precision are improved, but anchoring energy and stability deteriorate
Solution Approach 1:
The patent uses a composite material containing both selenide groups and diazo groups within the polyimide molecular structure. This composite approach combines the photo-alignability of diazo groups with the thermal stability and anchoring energy provided by selenide groups, resolving the contradiction between cleanliness and reliability
Solution Approach 2:
The patent modifies the molecular parameters of the polyimide by introducing specific side-chain structures containing selenide and diazo groups at controlled ratios (0.1-10 mol%). This parameter optimization allows tuning of both photo-alignment performance and thermal stability to achieve high anchoring energy while maintaining photo-alignment capability
2Stability of the object's composition
If traditional rubbing method is used to generate orderly channels, then alignment ability is improved, but dust generation and electrostatic damage increase
Solution Approach 1:
The patent replaces the mechanical rubbing method with a photochemical alignment method. Linearly polarized light induces photochemical reactions in the diazo groups, creating orderly molecular channels without mechanical contact, thereby eliminating dust generation and electrostatic damage while maintaining alignment ability
Solution Approach 2:
The patent introduces photo-sensitive diazo groups as intermediaries that mediate the alignment process. These groups undergo photochemical transformation under polarized light to create alignment channels, serving as a non-mechanical intermediary between light and liquid crystal molecules
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 polyimide achieves high photo-alignment stability and anchoring force, improving the performance and reliability of TFT-LCD displays, while being suitable for large-scale industrialization with reduced preparation costs.
Implementation Method 1
a photo-alignment method uses linear polarized light to induce the photochemical reaction of polymers on the surface of the layer
Data Source
AI summary
Disclosed are a polyimide and a display panel. A main chain of the polyimide includes at least one graft group, and the graft group is bonded with a first side-chain group and a second side-chain group. The graft group is selected from a phenyl group or a heterophenyl group, and the first side-chain group and the second side-chain group are bonded to the graft group in a meta-substitution manner. The first side-chain group is represented by a formula (1), and the second side-chain group is represented by a formula (2).