Structural control of polyvinyl chloride sealant layer for electrochromic switchable mirror glass based on Mg–Ni thin film

Abstract

We have been engaged in research and development of an electrochromic switchable mirror with a multilayer structure of Mg₄Ni/Pd/Al/Ta₂O₅/H_XWO₃/indium tin oxide (ITO) on a glass substrate. In our recent work, an as-prepared device was found to be easily degraded by environmental factors such as temperature and humidity, as shown by a degraded surface of the device. In this work, a polyvinyl chloride (PVC) layer was fabricated as a sealant layer for improving the environmental durability of the device. The structure of the layer could be controlled by adjusting the fabrication conditions such as the concentration of materials and rotational speed used in spin coating. The optical switching properties of the device with the sealant layer were also investigated. The sealant layer was fabricated using 1.25 wt % PVC solution in tetrahydrofuran at a rotational speed of 500 rpm. Although the device with the sealant layer had a thicker film, it showed superior optical switching properties even with a change in reflectance range due to multilayer interference. Furthermore, the device without the sealant layer easily degraded in an accelerated degradation test at a constant temperature of 40°C and a constant relative humidity of 80% after only 2 days. On the other hand, the surface of the device with the sealant layer showed no change in the same test. This result suggests that the PVC sealant layer has some advantages for preventing the environmental effects on the properties of the device.