Poly(amide-imide) Copolymer for Flexible Display Window Film
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Solution Overview
Problem
There is a need for polymers with excellent optical and mechanical properties for flexible display devices, as existing polyimide or poly(amide-imide) films face a trade-off between mechanical hardness and optical properties like light transmittance and yellowness index.
Innovation Solution
A poly(amide-imide) copolymer is developed using a tetracarboxylic acid dianhydride with an aliphatic acid dianhydride, a diamine with aromatic rings linked through functional groups, and an aromatic dicarboxylic acid derivative, optimizing the mole ratios to enhance mechanical properties like tensile modulus while maintaining high optical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a hard coating layer is applied to supplement hardness, then the hardness is improved, but the base film still requires high tensile modulus and the overall structure becomes more complex
Solution Approach 1:
The patent extracts the hardness-enhancing functional groups (aromatic rings, imide groups) from separate hard coating layers and incorporates them directly into the base film's polymer chain structure. This integration eliminates the need for additional hard coating layers while maintaining high hardness, thereby reducing structural complexity.
Solution Approach 2:
The patent merges the functions of the base film (providing flexibility and light transmittance) and the hard coating layer (providing hardness) into a single integrated poly(amide-imide) copolymer structure. The copolymer simultaneously delivers high tensile modulus, excellent optical properties, and high hardness without requiring multiple layers.
2Strength
If polymers with high tensile modulus are used to achieve high hardness, then the hardness is improved, but the optical properties like light transmittance and yellowness index deteriorate
Solution Approach 1:
The patent applies local quality by strategically placing rigid aromatic rings and imide groups at specific positions within the polymer chain to provide localized hardness enhancement, while the overall copolymer structure maintains good optical properties. The controlled incorporation of these rigid groups ensures high tensile modulus without excessive yellowness index.
Solution Approach 2:
The patent changes the chemical composition parameters of the polymer by incorporating specific aromatic diamines and tetracarboxylic acid dianhydrides in controlled ratios. This parameter optimization allows achieving high tensile modulus (≥6.5 GPa) while maintaining light transmittance (≥87.5%) and acceptable yellowness index.
Data Source
Figure 1~2
AI summary
According to an embodiment, provided is a poly(amide-imide) copolymer a reaction product of at least a tetracarboxylic acid dianhydride, at least a diamine, and at least a dicarboxylic acid derivative, wherein the at least a tetracarboxylic acid dianhydride comprises a tetracarboxylic acid dianhydride represented by Chemical Formula 1, the at least a diamine comprises a diamine represented by Chemical Formula 2, and the at least a dicarboxylic acid derivative comprises a dicarboxylic acid derivative represented by Chemical Formula 3: Chemical Formula 2 NH2-R2-NH2 wherein, R1 to R3, X1 and X2 are the same as defined in the specification.