Polyvinyl alcohol-based polarizers for new displays: molecules, processing and properties

Polarizers are a key component of new display panels (i.e. liquid crystal displays (LCDs) and organic light-emitting diodes (OLEDs)), consisting of a polarizing film, support film, compensation film, and optical clear adhesives between the layers. The key functional layer is the iodine-doped polyvinyl alcohol (PVA) film. The processing of polarizers involves the synthesis of an optical-grade PVA resin, followed by the preparation of highly oriented iodine-doped PVA films, which includes the film casting, iodine doping, boric acid crosslinking, and post-stretching steps. Revealing the multi-scale structure and changes in chain dynamics during processing is crucial for establishing the structure-process-property relationship of PVA-based polarizers. The current work reviews the recent research progress in this direction, primarily including the following: (1) primary chemical structure of PVA, (2) solution casting of PVA films, (3) hierarchical structure and dynamics heterogeneity of plasticized PVA films, (4) formation mechanism of PVA-iodine complexes, and (5) crosslinking mechanism of boric acid in PVA.