Preparation Of Poly (Vinyl Alcohol)-Iodine Polarizing Film And Studies Of Its Performance

Polarizer is a kind of optical film which converts the non-polarizing light into polarizing light. Polarizer is a multiple film, also a laminated film including the polarizing film, protective film and pressure sensitive adhesive. As to polarizer, the polarizing film is a critical and essential component, which directly dominates the optical performance of polarizer. At present, all the high-class polarizer in the market has been made in Japan and Korea. The polarizer made in china can merely meet the demands for the low-end products.Dichroic polarizer mainly contains the iodine-based and dye-based film. Polyvinyl alcohol (PVA)/iodine polarizing films are extensively employed owing to its high optical performance that it easily attains99.9%degree of polarization and42%transmittance. Whereas the PVA/dye polarizing films are remarkable for its resistance of humidity and heat. According to stretching process, there have dry-stretching process and wet-stretching process of polarizing films which signify the PVA film is been stretched at some kind atmosphere and in the solutions.In this study, PVA/iodine polarizing film is prepared, we optimize the conditions of stretching, anticipate to obtain the best product. Finally, the film is stabilized with boric acid to elevate the durability to thermal and humid intrusion.The precursor film is manufactured by casting the PVA/iodine solution, uniaxially stretched with a testing machine, then soaked the film in saturated boric acid aqueous solution. The temperature, speed and ratio of stretching process are investigated which can determine the optical performance, and the mechanism of the film is also analyzed. At the same time, the temperature and time of dip process also are evaluated which can decide the stability and mechanical performance. The best polarizing film can be acquired when the temperature, speed and ratio are fixed to100℃,10mm/min and5, respectively. We can balance the cross-linking effect and efficiency of production when the temperature of saturated boric acid aqueous solution is setting at70℃, the dip time is limited to5minutes.The transmittance (T) is measured using the UV visible (UV-VIS) spectrometry for wavelengths from400-700nm, the degree of polarization is calculated through the following equation:P(?)=(?1/2×100. In this equation, T(?) and T(?) are the transmittances of the film that are superimposed on each other parallel and perpendicular to the direction of the elongation of the film, respectively. The X-ray diffraction (XRD) is measured to investigate the inner molecular structure of PVA chains. The differential scanning calorimetry (DSC) was performed to examine the switch between crystalline and amorphous portions. The thermal gravimetry analysis (TGA) is carried out to assess the heat stability of film At last, the polarizing film is placed into a constant temperature and humidity (80℃,90%), the durability of polarizing film is demonstrated with respect to the change in the degree of polarization and transmittance.