Polyimide Film Surface Smoothness via Viscosity Control
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Solution Overview
Problem
Conventional methods for producing polyimide films struggle to achieve high surface smoothness, which is crucial for applications like organic electroluminescence (EL) to prevent short circuits due to high surface roughness.
Innovation Solution
A method involving the preparation of a polyamic acid solution with a viscosity of 5 to 150 cps by reacting a tetracarboxylic dianhydride and an aromatic diamine, followed by adding a compound to form a polyimide film with a specific repeating unit, allowing for imidization to create a smooth and flexible film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional methods are used to produce polyimide films, then the films can be manufactured with basic properties, but the surface smoothness is insufficient leading to high surface roughness
Solution Approach 1:
The patent applies parameter changes by controlling the viscosity of the polyamic acid solution within a specific range (5-150 cps) and managing the total content of tetracarboxylic dianhydride and aromatic diamine (15% by mass or less). These parameter optimizations enable the solution to form films with superior surface smoothness (Ra 0.1 μm or less) while maintaining ease of manufacture through standard coating and imidization processes
2Manufacturing precision
If the viscosity of polyamic acid solution is reduced to improve coating workability and surface smoothness, then coating quality improves, but the solution becomes difficult to maintain adequate mechanical strength
Solution Approach 1:
The patent resolves this contradiction by precisely controlling the viscosity parameter within 5-150 cps and the total solid content at 15% by mass or less. This optimized parameter range ensures the solution remains fluid enough for excellent coating workability and surface smoothness while maintaining sufficient mechanical strength through proper composition balance
Solution Approach 2:
The patent uses a composite approach by combining tetracarboxylic dianhydride and aromatic diamine in specific proportions within the controlled viscosity range. This composite composition achieves both low viscosity for smooth coating and adequate mechanical strength for film integrity
3Strength
If aromatic polyimides are used to achieve flexibility and heat resistance, then mechanical properties improve, but light-transmitting properties deteriorate due to brown coloration
Solution Approach 1:
The patent employs a composite material approach by synthesizing polyimides from tetracarboxylic dianhydride and aromatic diamine components. This specific composite structure achieves a balance between heat resistance and light transparency, producing films with high heat resistance while maintaining excellent light-transmitting properties unlike conventional brown-colored aromatic polyimides
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
This approach enables the efficient production of polyimide films with higher surface smoothness, reducing the risk of short circuits and enhancing their suitability for applications requiring low surface roughness.
Implementation Method 1
reacting the tetracarboxylic dianhydride and the aromatic diamine with each other in the raw material mixture liquid to form a polyamic acid
Implementation Method 2
followed by imidization to create a smooth and flexible film
Data Source
AI summary
A method for producing a polyimide film includes: obtaining a polyamic acid solution having a viscosity of 5 to 150 cps by preparing a raw material mixture liquid containing a solvent, a tetracarboxylic dianhydride represented by a specific general formula, and an aromatic diamine represented by a specific general formula, and has a total content of the tetracarboxylic dianhydride and aromatic diamine of 15% by mass or less, and reacting the tetracarboxylic dianhydride and aromatic diamine with each other in the raw material mixture liquid forming a polyamic acid having a repeating unit represented by a specific general formula; obtaining a polyimide-forming mixture liquid by adding a compound represented by a specific general formula to the polyamic acid solution; and obtaining a polyimide film represented by a specific general formula by forming a film made of the polyimide-forming mixture liquid, followed by imidization of the polyamic acid in the film.