Polyimide Composition for Optical Devices with Low Anisotropy
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Solution Overview
Problem
Polyimides with high aromatic ring content exhibit yellow colors, leading to low transmittance and high birefringence, making them unsuitable for optical applications due to low coefficient of thermal expansion, high heat resistance, and high optical anisotropy.
Innovation Solution
A composition comprising a tetracarboxylic dianhydride mixture with a planar structure and a tilted dihedral structure, combined with 2,2'-bis(trifluoromethyl)benzidine, which inhibits chain alignment and charge transfer complex formation, resulting in a polyimide with high transparency and low optical anisotropy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If polyimides with high aromatic ring content are used, then heat resistance and low coefficient of thermal expansion are improved, but transmittance decreases and optical anisotropy increases
Solution Approach 1:
The patent changes the molecular structure parameters of the polyimide by incorporating specific tetracarboxylic dianhydride units ( Chemical Formulae 5 and 7) with particular dihedral angles. This structural parameter change allows the material to maintain heat resistance while reducing optical anisotropy and improving transmittance, as the specific molecular geometry disrupts chain alignment and charge transfer complex formation.
Solution Approach 2:
The patent creates a composite polyimide structure by combining different tetracarboxylic dianhydride units (Chemical Formulae 5 and 7) with 2,2'-bis(trifluoromethyl)benzidine. This composite approach at the molecular level achieves synergistic effects where the combination of specific structural units provides both thermal stability and improved optical properties that neither component could achieve alone.
2Temperature
If polyimides with high aromatic ring content are used, then heat resistance is improved, but optical anisotropy increases
Solution Approach 1:
The patent modifies the molecular structure parameters by using tetracarboxylic dianhydrides with specific dihedral angles (Formulae 5 and 7). This structural change reduces optical anisotropy while preserving heat resistance, as the specific geometry prevents favorable packing and charge transfer complex formation that would otherwise increase optical anisotropy.
Solution Approach 2:
The patent employs a composite molecular structure combining specific tetracarboxylic dianhydride units with 2,2'-bis(trifluoromethyl)benzidine. This molecular-level composite creates a polyimide that simultaneously achieves high heat resistance and low optical anisotropy through the synergistic arrangement of different structural units.
3Ease of manufacture
If conventional polyimide compositions are used, then manufacturing simplicity is maintained, but transmittance and optical clarity deteriorate
Solution Approach 1:
The patent changes the chemical composition parameters by incorporating specific tetracarboxylic dianhydride units (Chemical Formulae 5 and 7) in defined ratios. This compositional change improves transmittance and reduces yellowness index while maintaining compatibility with conventional polyimide manufacturing processes, requiring only adjustments to原料 composition rather than fundamental process changes.
Data Source
Figure 1
AI summary
A composition for preparing a polyimide including a tetracarboxylic dianhydride mixture including a tetracarboxylic dianhydride represented by Chemical Formula 1A, Chemical Formula 1 B, or a combination thereof, a tetracarboxylic dianhydride represented by Chemical Formula 2, and a diamine represented by Chemical Formula 3: Chemical Formula 3 NH2-R1-NH2 wherein in Chemical Formulae 1A, 1 B, 2 and 3, definitions of groups and substituents are described in the specification.