Polyphenylene Films for Flexible OLED Displays
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Solution Overview
Problem
Conventional polymeric optical films used in flexible displays, such as polyolefin and polyester films, exhibit poor thermal and dimensional stability, while high-temperature polymer films like polyimides have a colored appearance and poor optical transparency, making them unsuitable for modern flexible OLED displays.
Innovation Solution
Oriented films comprising kinked rigid-rod polyphenylene polymers, which are mono- or biaxially oriented, providing high light transmittance, low yellowness, and high hardness, are used as substrates in flexible displays, overcoming the limitations of existing films by incorporating at least 95% 1,4-linkages and pendant solubilizing side groups.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional polymeric optical films (polyolefin and polyester) are used, then ease of manufacture is improved, but thermal stability and dimensional stability deteriorate
Solution Approach 1:
The patent changes the chemical composition parameters by using polyphenylene polymers with specific 1,4-linkage structures and pendant solubilizing side groups, achieving high thermal stability (maintaining mechanical properties at temperatures up to 200°C) while maintaining manufacturability through solution casting and orientation processes
2Stability of the object's composition
If standard high-temperature polymer films (polyimides) are used, then thermal stability is improved, but optical transparency and color appearance deteriorate
Solution Approach 1:
The patent applies local quality by introducing pendant solubilizing side groups at specific positions on the polyphenylene polymer chains, which locally modify the molecular packing and electronic structure to reduce yellowing and improve optical transparency while maintaining the high thermal stability of the aromatic polymer backbone
Solution Approach 2:
The patent changes the chemical structure parameters by using predominantly 1,4-linkages (at least 90 mol%) in the polyphenylene polymer, which creates a more linear and regular structure that reduces intermolecular interactions causing yellowing, achieving both high thermal stability and excellent optical transparency with yellowness index below 4.0
3Strength
If oriented films are used, then hardness and dimensional stability are improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by incorporating pendant solubilizing side groups into the polymer structure before film formation, which pre-establishes molecular spacing and orientation tendencies that facilitate subsequent orientation processing and achieve high hardness without requiring complex multi-step manufacturing procedures
Data Source
AI summary
The present invention relates to hard optically transparent films suitable as protective films for displays, in particular flexible OLED displays.