Polyimide-Polybenzoxazole Copolymer Film for Flexible Electronics
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Solution Overview
Problem
Current polymer films used in flexible substrates and protective films for electronic devices face challenges with poor thermal stability and optical properties, such as high coefficient of thermal expansion and low transparency, which affect their performance and reliability.
Innovation Solution
A transparent film made from a polyimide-polybenzoxazole copolymer with a specific repeating unit structure, which includes a mole ratio of imide to benzoxazole units, is developed, offering improved thermal and optical properties, including high transmittance, low yellow index, and reduced thermal expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional polymer films are used for flexible substrates and protective films, then they are lightweight and easy to process, but they exhibit poor thermal stability with high coefficient of thermal expansion
Solution Approach 1:
The patent employs a composite polymer structure combining polyimide and polybenzoxazole segments in a single copolymer chain. This composite approach leverages the thermal stability of polyimide while incorporating the low thermal expansion characteristics of polybenzoxazole, achieving a material that simultaneously provides both required properties that conventional single-polymer films cannot deliver
Solution Approach 2:
The patent systematically varies the compositional parameters of the copolymer, specifically controlling the weight ratio of polyimide to polybenzoxazole units (where polybenzoxazole content is 5-50 wt%). By adjusting this parameter, the patent optimizes the balance between thermal stability and coefficient of thermal expansion, demonstrating that precise compositional control enables tailoring of thermal properties to meet specific application requirements
2Illumination intensity
If conventional polymer films are used for flexible substrates and protective films, then they are lightweight and easy to process, but they exhibit poor optical properties with low transparency and high yellow index
Solution Approach 1:
The patent controls the compositional parameters of the copolymer, specifically maintaining polybenzoxazole content within 5-50 wt% and using specific monomer ratios during polymerization. This parameter optimization ensures the film achieves high transparency (greater than 85% in the visible range) while keeping the yellow index low (less than 5.2), balancing optical clarity with color stability
Solution Approach 2:
The patent introduces functional heterogeneity at the molecular level within the copolymer chain, where polyimide units provide structural backbone and polybenzoxazole units contribute to optical clarity and color stability. This local differentiation of functional units within the single polymer material enables simultaneous achievement of mechanical strength, transparency, and low yellowing without requiring multiple separate layers or coatings
3Reliability
If deposition films are formed on conventional polymer films, then surface protection is achieved, but surface wrinkles occur due to thermal expansion mismatch
Solution Approach 1:
The patent specifically designs the copolymer to have a low coefficient of thermal expansion (5-20 ppm/°C) that closely matches typical deposition films such as silicon oxide, silicon nitride, or metal layers. This thermal expansion matching prevents the formation of surface wrinkles and delamination during deposition processes and subsequent thermal cycling, ensuring reliable surface protection without the defects that plague conventional polymer substrates
Solution Approach 2:
The copolymer structure combines polyimide's mechanical strength and polybenzoxazole's dimensional stability, creating a composite material that provides both structural integrity and thermal compatibility with deposition films. This composite nature enables the substrate to withstand the thermal stress of film deposition while maintaining a smooth surface morphology
Data Source
AI summary
A film including a polyimide-polybenzoxazole copolymer including a repeating unit represented by Chemical Formula 1:wherein in Chemical Formula 1, A1, A1′, A2, A3, m, and n are the same as described in the specification.