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

Abstract

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.