Polyimide Film with Norbornane Rings for Low Thermal Expansion
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Solution Overview
Problem
Current polyimides with alicyclic tetracarboxylic dianhydride and aromatic diamine components face challenges in achieving high transparency, bending resistance, and low coefficient of linear thermal expansion, especially at high temperatures, which hinders their use in forming fine circuits and substrates for displays and touch panels.
Innovation Solution
A polyimide precursor comprising specific repeating units, such as those represented by chemical formulas (1) to (6), which include norbornane rings reacting with amino groups to form amide or ester bonds, is used to create a polyimide with a low coefficient of linear thermal expansion and high heat resistance, allowing for improved substrate formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a semi-alicyclic polyimide is used to achieve transparency and bending resistance, then transparency and flexibility are improved, but the coefficient of linear thermal expansion becomes too high (50 ppm/K or more)
Solution Approach 1:
The patent changes the chemical structure parameters of the polyimide by introducing specific cyclic structures (norbornane rings) and controlling the composition ratios of different repeating units. This structural parameter change reduces the coefficient of linear thermal expansion to 50 ppm/K or less while maintaining transparency and flexibility, resolving the contradiction between optical properties and thermal stability.
2Stability of the object's composition
If a polyimide with low coefficient of linear thermal expansion is used to prevent warpage, then dimensional stability is improved, but the glass-transition temperature becomes too high (about 300°C), causing film softening at high temperatures
Solution Approach 1:
The patent introduces different types of repeating units with distinct local structural characteristics into the polyimide chain. Unit (1) with norbornane rings provides low thermal expansion, while units (2) and (3) with different structural features moderate the glass-transition temperature. This local structural differentiation allows the material to achieve both dimensional stability and appropriate thermal transitions.
3Manufacturing precision
If a polyimide is used to form fine circuits and substrates, then manufacturing capability is improved, but warpage occurs at high temperatures due to high coefficient of linear thermal expansion
Solution Approach 1:
The patent creates a composite polyimide structure by combining multiple repeating units (units (1), (2), and (3)) with different functional characteristics in specific ratios. Unit (1) provides low thermal expansion, while units (2) and (3) contribute to film formation properties and thermal stability. This composite approach enables both fine circuit manufacturing capability and warpage resistance at high temperatures.
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 polyimide exhibits high transparency, bending resistance, and a low coefficient of linear thermal expansion, facilitating the formation of fine circuits and substrates for display and touch panel applications without warpage issues at high temperatures.
Implementation Method 1
norbornane rings reacting with amino groups to form amide or ester bonds
Data Source
AI summary
A polyimide precursor comprising at least one repeating unit represented by the following chemical formula (5):in which A3 is a divalent group of an aromatic diamine or an aliphatic diamine, from which amino groups have been removed; and X3 and Y3 are each independently hydrogen, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms, and/or at least one repeating unit represented by the following chemical formula (6):in which A3 is a divalent group of an aromatic diamine or an aliphatic diamine, from which amino groups have been removed; and X4 and Y4 are each independently hydrogen, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms.