Effect of fluorination on haze reduction in transparent polyimide films for flexible substrates

Abstract

High transmittance is an important parameter for polyimide (PI) films used as flexible display substrates. However, thermal treatment during film fabrication can cause an undesired phenomenon affecting color change in the films, which is called haze. Until now, haze formation in PI films has remained mostly unexplored, suggesting that originates in the composition. In this work, the effect of fluorination on haze reduction was investigated. Both experiments and density functional theory calculations suggest that a high degree of fluorination of PI repeating units results in weaker intra/intermolecular conjugations between polymer chains and higher haze resistance in the following order: one fluorinated group (−1.43 eV) > two fluorinated groups (−0.76 eV) > three fluorinated groups (−0.52 eV) > four fluorinated groups (−0.43 eV). The differences in the haze resistance can influence on haziness in the PI films by thermal gradient inside a lab scale cavity in a furnace. The obtained results indicate that slow heat transfer facilitates the manufacturing process to obtain high transparency in PI films. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44375.

Reduced Coefficients of Linear Thermal Expansion of Colorless and Transparent Semi-Alicyclic Polyimide Films via Incorporation of Rigid-Rod Amide Moiety: Preparation and Properties

“…Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectra of the SPI ALs were recorded on a Iraffinity-1S FT-IR spectrometer (Shimadzu, Kyoto, Japan). Nuclear magnetic resonances ( 1 H-NMR) were performed on an AV 400 spectrometer (Ettlingen, Germany) operating at 400 MHz in DMSO-d 6 . Ultraviolet-visible (UV-Vis) spectra were recorded on a Hitachi U-3210 spectrophotometer (Tokyo, Japan) at room temperature.…”

“…The structural factors that can improve the thermal stability of polymer films often reduce the optical properties of the films at the same time, and vice versa. Thus, it is a changeling research topic to develop polymer optical films with both of excellent thermal stability and good optical transparency [5][6][7].In recent years, the research progress of colorless and transparent polyimide (CPI) films has attracted great attention in the research and development of high performance polymer optical films [8][9][10]. Based on the previous decades of research on the origination of coloration in traditional all-aromatic PI films, the researchers revealed many effective procedures to prohibit the formation of intra-or intermolecular charge transfer complexes (CTC) between the electron-donating diamine moiety and the electron-accepting dianhydride moiety so as to improve the optical transparency of the PI films [11][12][13].…”

“…The structural factors that can improve the thermal stability of polymer films often reduce the optical properties of the films at the same time, and vice versa. Thus, it is a changeling research topic to develop polymer optical films with both of excellent thermal stability and good optical transparency [5][6][7].…”

“…depicts the 1 H-NMR spectra of the PI resins purified by several dissolution-precipitation circulations followed by dried at 100 • C in vacuum together with the assignments of individual proton. All the resins were soluble in the NMR solvent, DMSO-d6 and clear absorptions for hydrogenPolymers 2020, 12, 413 7 of 15…”

Synergistic effect of thermoplastic phenolic resin and multiwalled carbon nanotubes on the crystallization of polyoxymethylene

“…The POM bars should also be extruded very slowly without pulling and depending only on the pressure of the head part of the extruder, and must be shaped in an oil bath of 125-135 C. Most importantly, due to the high crystallinity with coarse crystalline grains, the POM articles are very brittle. [3,8] Therefore, the crystallization behavior, including crystallization kinetics [2,[10][11][12][13][14][15][16][17][18][19][20][21][22] and nucleation, [23][24][25][26] as well as the toughness [3,[27][28][29][30][31][32][33][34][35][36][37][38] of POM, have always been its main research fields.…”