Low Temperature Deposition of ZnO SiO 2 Thin Films on Polymer Surfaces by Plasma Enhanced CVD
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Low Temperature Deposition of ZnO SiO2 Thin Films on Polymer Surfaces by Plasma Enhanced CVD Hidetaka. Anma1,2, Yuuji. Yoshimoto1 , Mariko. Tanaka1, Hiroyuki Takatsuka1, and Yoshinori. Hatanaka2, 1 Koito Manufacturing Co.,Ltd 500,Kitawaki,Shimizu,424-8764,Japan. 2 Research Institute of Electronics, Shizuoka University, Hamamatsu, 432-8011,Japan ABSTRACT ZnO and SiO2 thin films coated on plastic materials were investigated for the protection against solar ultraviolet (UV) radiation and the hard coating. Using diethylzinc (DEZ) as the organic zinc material, we attempt to deposit ZnO thin films on polycarbonate (PC) resin at room temperature by the cathode deposition technique of the plasma enhanced (PE) CVD method. It was found that the rf power and the substrate temperature intensively influenced on the deposition rate. The deposition rate increased with the rf power up to 100W, but decreased with the RF power above 100W, and also decreased with increasing the substrate temperature. In a xenon arc weatherability test, the ZnO-coated PC plates exhibited remarkable protection characteristics against UV radiation. They kept a smooth surface and no- coloring even if UV light irradiated for 1000 hours. Moreover, SiO2 film deposited from tetraethoxysilane (TEOS) was over-coated on the ZnO film / PC plates. These films showed a drastic improvement in the hardness. Therefore, these films are expected as the UV-cut and hard coating for the automotive parts. INTRODUCTION To reduce the vehicle weight, thermoplastic resins are increasingly introduced to automotive parts. In the environmental aspect, recycle uses are strongly required. In particular, polycarbonate (PC) resins are used as lens materials for automotive headlamps. However, these resins have weakness for the degradation such as discoloration, deformation surface roughness caused by heating and ultraviolet (UV) light and water. For solving the disadvantages, the coating technologies have been developed for the plastic parts to be coated with protective paints on their surface. However, these painting methods have disadvantages for the release of the polluting organic solvent to the atmosphere. Therefore, it is required to develop a new surface treatment technology, which provides a uniform high-quality coating in the point of view of the soft-environment. [1-3]. Recently we attempted to coat the ZnO and SiO2 thin films on PC resin plates by the plasma enhanced (PE) CVD, which is consisted of capacitively coupled electrodes connected which rf source (13.56MHz). In this paper, we report the film characteristics and deposition conditions for the application to the UV-cut and hard coating for the PC resins. EXPERIMENTAL ZnO thin films generally are prepared by means of the thermal CVD, rf sputtering, reactive sputtering, sol-gel chemical synthesis method and so on. [4-6] In these methods, considerable high processing temperatures or substrate temperatures above 300 are usually required. On the point of view of plastic resin coating, it is necessary to be developed the low
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