Polyamide-imide Film Transparency and Strength via Local Quality
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Solution Overview
Problem
Existing polyimides used in display areas face challenges with colorlessness, transparency, and high thermal expansion coefficients, which affect their suitability for flexible displays requiring mechanical strength, solubility, and thermal stability.
Innovation Solution
A polyamide-imide with specific repeating structures and a manufacturing method involving tetracarboxylic dianhydrides and diamines is developed, incorporating fluoroalkyl groups and cyclo-olefin structures to enhance transparency and mechanical properties, reducing charge transfer complexes and thermal expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If aromatic polyimide is used to provide mechanical strength and thermal stability, then mechanical properties and heat resistance are improved, but colorlessness and transparency deteriorate due to charge transfer complex formation
Solution Approach 1:
The patent introduces different types of rigid rod structures (aromatic rings, cyclo-olefin structures) at specific positions within the polymer chain to create local variations in electron density and charge transfer characteristics, achieving both strength and transparency
Solution Approach 2:
The patent creates a composite polymer structure combining polyimide and polyamide-imide segments with different functional groups (aromatic rings, cyclo-olefin structures, fluoroalkyl groups) to achieve synergistic effects of mechanical strength and optical transparency
2Temperature
If polyimide is used to provide thermal stability, then heat resistance is improved, but thermal expansion coefficient increases which is unsuitable for flexible displays
Solution Approach 1:
The patent changes the molecular structure parameters by introducing cyclo-olefin structures and fluoroalkyl groups with different thermal expansion characteristics to reduce the overall thermal expansion coefficient while maintaining thermal stability
3Strength
If polyimide is used to provide mechanical strength, then strength is improved, but solubility deteriorates making solution casting difficult
Solution Approach 1:
The patent introduces flexible alkylene groups and fluoroalkyl groups at specific positions in the polymer chain to create local regions with different solubility characteristics, improving overall solubility while maintaining mechanical strength
Solution Approach 2:
The patent changes the chemical composition parameters by incorporating fluoroalkyl groups and adjusting the ratio of rigid rod structures to flexible segments, optimizing the balance between mechanical strength and solubility for solution processing
4Illumination intensity
If electron-withdrawing functional groups are introduced to reduce charge transfer complex and improve transparency, then transparency is improved, but mechanical strength may be compromised
Solution Approach 1:
The patent introduces electron-withdrawing fluoroalkyl groups at specific positions rather than throughout the entire chain, creating local regions with reduced charge transfer while maintaining overall mechanical integrity through the rigid rod structure
Solution Approach 2:
The patent creates a composite structure combining electron-withdrawing groups (for transparency) with rigid aromatic and cyclo-olefin structures (for mechanical strength), achieving synergistic effects
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 resulting polyamide-imide film exhibits improved mechanical strength, heat resistance, and transparency, making it suitable for applications like flexible displays, optical films, and IC packages with reduced yellowness and thermal expansion.
Implementation Method 1
it can be explained by the theory of charge transfer complex (hereinafter, called CT-complex) induced by π electrons of benzene within a main chain of the polyimide
Implementation Method 2
introducing a cyclo-olefin structure instead of benzene to the main chain of the polyimide can reduce π electron density to manufacture a colorless transparent polyimide film
Implementation Method 3
a method of introducing an electron-withdrawing functional group having relatively strong electronegativity such as trifluoromethyl (-CF 3 ), sulfone (-SO 2 ) and ether (-O-) to the main chain of the polyimide is used to lower resonance effect by limiting the movement of π electrons
Data Source
AI summary
Provided in the present invention is a polyamide-imide film having significantly enhanced mechanical physical properties and heat resistance while maintaining transparency. The polyamide-imide has excellent transparency, heat resistance, mechanical strength and flexibility, and thus can be used in a variety of fields including a device substrate, a cover substrate for a display, an optical film, an integrated circuit (IC) package, an adhesive film, a multilayer flexible printed circuit (FPC), a tape, a touch panel, and a protection film for an optical disk.