Polarizer effect and structure of iodinated before and after casting poly(vinyl alcohol) film

Abstract

Poly(vinyl alcohol) (PVA)/iodine polarizing film was manufactured as follows: PVA iodinated in solution before casting (IBC film) and iodinated again after casting (IBC þ IAC film) and then the IBC þ IAC film was drawn in boric acid aqueous solution (IBC þ IAC polarizing film), to improve the durability of the polarizing film under a humid and warm atmosphere. These effects were examined by investigating the structural and optical properties of the IBC, IBC þ IAC, and IBC þ IAC polarizing films. In the IBC state, the PVA chain segments that combined boric acid and iodine were regarded as defects of the crystal, the formation of I 3 À decreased with respect to weight gain of boric acid. In the IBC þ IAC state, the strength of the peak corresponding to I 3 À decreased and the I 5 À peak increased. The iodine ions penetrated into crystal of the IBC state during the IAC process and formed a new PVA/iodine complex crystal at the 2y ¼ 20 in the X-ray diffraction curves. In the IBC þ IAC polarizing film state, another type of polarizing film (IBC þ IAC polarizing film-H) containing I 3 À ions mainly was manufactured as well as the IBC þ IAC polarizing film to compare the effects of the I 3 À and I 5 À ions on the durability of the polarizing films. The durability of the I 3 À ions that were complexed with the PVA chain was higher than the I 5 À ions, which could possibly be separated to I 3 À and I 2 .

Effect of boric acid treatment method on the characteristics of poly(vinyl alcohol)/iodine polarizing film

“…The DSC thermograms of the untreated PVA films show the endothermic peak at 230°C and starting endothermic peak at around 280°C, corresponding to the melting of crystals and the partial decomposition of OH side groups, respectively. However, the PVA/iodine or PVA/iodine/boric acid complex films indicated a new broad peak at the lower temperature zone (60°C–150°C), which was probably assigned to melting of the quasicryatalline phase 12. The peak temperature increased with adding the boric acid (I‐B, B‐I, and I+B), especially that of I‐B film highest.…”

“…In study of examination of the role of boric acid and the effect of heat treatment on PVA–iodine polarizing films prepared IBC of PVA/iodine/boric acid films, the transmittance and degree of polarization for the films increased and decreased with increasing heat treatment time under heat and a humid atmosphere, respectively. However, this tendency decreased with increasing boric acid concentration and heat treatment 12. These results indicate that boric acid on preparing IBC PVA/iodine polarizing sheet film enhances the formation of I 3 − /I 5 − ions and increases the durability under heat and humid atmosphere.…”

“…In our previous studies, we have estimated the effect of boric acid on durability of PVA–iodine polarizing sheet film12, 13 in the iodination at solution before casting (IBC); boric acid combined with the PVA chain to form intramolecular crosslinking segments that were regarded as a defect in the crystal, which decreased the melting temperature of PVA. The formation of I 3 − and I 5 − increased with increasing boric acid content in IBC state.…”

Non-invasive biopsy of doped-ions inside optical substrate by modified two-photon microscopy

“…The clustered Iodine-ions diffuse easily to the TAC layer over time and thus the polarization properties can easily vanish. This will lead to degradation of the contrast ratio and hue balance in liquid-crystal displays [11]. It is important to measure the depth-dependent Iodine traces during the fabrication process of the polarizer in real time, because the fabrication process could be terminated to save cost and time if unusual axial Iodine distributions are observed.…”

“…When low-gap dopants are not uniformly dispersed in the emissive layer of OLED devices, this can lead to spatial variation in the color of the white electroluminescence, affecting lighting applications. The spatial distribution of Iodine-dye in PVA polymer films may be helpful for extracting and mapping more properties of a polarizer [10,11].…”