Poly(amide-imide) Copolymer Film for Flexible Display Windows

The patent applies this principle by developing a polyimide-based flexible protective film that replaces rigid glass with a flexible polymer structure. The film incorporates specific molecular configurations (cyclic structures and cross-linking points) that provide both flexibility for bending applications and adequate mechanical strength through controlled cross-linking density, enabling the display device to be bent or folded while maintaining protection.

The patent applies this principle by creating a composite polyimide structure combining different functional units within the same polymer chain. The film integrates rigid cyclic structures (for strength and dimensional stability) with flexible aliphatic chains (for bendability), and uses controlled cross-linking to balance these opposing requirements, achieving a material that simultaneously provides mechanical protection and flexibility.

The patent applies this principle by designing a flexible polyimide film with specific molecular architecture that includes flexible spacers and controlled cross-linking. The film achieves adequate mechanical strength not through rigidity but through optimized flexible structure with strategic cross-linking points, maintaining flexibility while providing sufficient protection for bendable displays.

The patent applies this principle by precisely controlling molecular parameters of the polyimide film, including the ratio of cyclic to linear structures, cross-linking density, and molecular weight distribution. By adjusting these parameters, the film achieves the optimal balance between flexibility and mechanical strength required for flexible display applications.

The patent applies this principle by implementing localized cross-linking at specific positions within the polyimide molecular structure rather than uniform cross-linking throughout. The cross-linking points are strategically placed at cyclic structures while maintaining flexible spacers between them, providing mechanical strength locally where needed while preserving optical transparency in the bulk material.

The patent applies this principle by precisely controlling the cross-linking degree as a critical parameter, maintaining it within a specific range (0.1-10 mol%) to achieve the optimal balance. Below this range, mechanical strength is insufficient; above this range, optical characteristics deteriorate. The patent also controls the type and distribution of cross-linking structures to minimize impact on light transmittance.