Yang Yang, Zheng Ziyuan, Lin Jun, Zhou Lintao, Chen Guohua
College of Materials Science and Engineering, Huaqiao University, Xiamen 361021, China.
Polymers (Basel). 2022 Mar 30;14(7):1413. doi: 10.3390/polym14071413.
Polarizer is a key component of the liquid crystal display panel, and the optical properties mainly include transmittance, degree of polarization and chromaticity. Polarizer is made of a multilayer optical film, in which the PVA polarizing film is the core structure for realizing the polarization of the whole polarizer. PVA polarizing film is commonly manufactured through a multi-step craft, including rinsing, dyeing, stretching and correcting. The correction process has a significant impact on the final apparent color and optical properties of the polarizer. In this study, the KI concentration in the correcting tank, ranging from 1% to 3%, was systematically investigated. With the increase in KI concentration, the Raman vibration peak at 160 cm representing I5- ions gradually weakened, while the Raman vibration peak at 110 cm representing I3- ions gradually increased, indicating that the KI in the correcting tank changed the chemical equilibrium of polyiodide ions in PVA. Then abundant chromophore I5- ions were consumed and I3- ions generated, so that the apparent color of PVA polarizing film gradually changed from dark blue to dark gray, and the chromaticity -value and -value gradually increased. The change in the concentration of dichroic species (I5- and I3-) in PVA polarizing film had directly affected its transmittance in the visible range. From the UV-Vis transmittance spectrum of PVA polarizing film, when the I5- ions were consumed and I3- ions generated, the transmittance of PVA polarizing film in the region of 675-525 nm wavelength increased gradually while the polarization degree also increased.
偏光片是液晶显示面板的关键组件，其光学性能主要包括透过率、偏振度和色度。偏光片由多层光学膜制成，其中聚乙烯醇（PVA）偏光膜是实现整个偏光片偏振的核心结构。PVA偏光膜通常通过多步工艺制造，包括冲洗、染色、拉伸和校正。校正过程对偏光片的最终表观颜色和光学性能有重大影响。在本研究中，系统地研究了校正槽中碘化钾（KI）浓度在1%至3%范围内的情况。随着KI浓度的增加，代表I5-离子的160 cm处的拉曼振动峰逐渐减弱，而代表I3-离子的110 cm处的拉曼振动峰逐渐增加，这表明校正槽中的KI改变了PVA中多碘离子的化学平衡。然后大量的发色团I5-离子被消耗，I3-离子生成，使得PVA偏光膜的表观颜色逐渐从深蓝色变为深灰色，并且色度a值和b值逐渐增加。PVA偏光膜中二色性物种（I5-和I3-）浓度的变化直接影响了其在可见光范围内的透过率。从PVA偏光膜的紫外-可见透过率光谱来看，当I5-离子被消耗且I3-离子生成时，PVA偏光膜在675 - 525 nm波长区域的透过率逐渐增加，同时偏振度也增加。
