P‐10.3: Research on Mechanical Property of Colorless Polyimide Cover Film for Foldable OLED Display

In the field of flexible display, colorless polyimide (CPI) cover film is composed of colorless polyimide base film and hard coating (HC). At low temperature, after the display module is folded outward for thousands of cycles, the cover film is prone to crack, resulting in the failure of module reliability. Therefore, this paper focuses on the mechanical properties of A manufacturer's CPI cover film at room temperature and low temperature (‐20℃). The study shows that the elongation of the cover film decreases from 11% at room temperature to 6.9% at low temperature; the elongation of the hard coating decreases from 5%‐6% at room temperature to 3% at low temperature. This will lead to cover film cracks or fractures after the module is folded outward at low temperature. After the manufacturer improved the ductility of the cover film, the elongation of improved sample can be increased from 11% to 21%; the elongation of hard coating can be increased from 5%‐6% to 11%‐13%. The module used improved sample can successfully pass 20,000 cycles at low temperature. In addition, the properties, micromorphology and elemental composition of the sample were characterized by tensile testing, DMA and TEM, which can explain the improvement mechanism.