Preparation of Hard Coatings on Polycarbonate Substrate by High Frequency Ion Beam, Deposition using CH 4 /H 2 Gases
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* SamYang R&D Center, 63-2 Whaam-dong, Yusung-gu, Taejon, Korea "**Departmentof Materials Science, Korea University, Sungbuk-gu, Seoul, Korea ABSTRACT Polycarbonate is one of the most widely used engineering plastics because of its transparency and high impact strength. The poor wear and scratch properties of polycarbonate have limited its application in many fields. In order to improve the wear and scratch properties of polycarbonate we have deposited diamond like carbon (DLC) coatings. The diamond like carbon coatings were made using a high frequency ion beam gun by introducing H2 and CH4 gases. The coatings were characterized with scanning electron microscope, Raman spectroscopy, ellipsometer, and microscratch tester. Polymer hard coating was applied onto the polycarbonate substrate before depositing a diamond like carbon coating to see the effect of interlayer on the system's failure mechanism. INTRODUCTION Polycarbonate has an unusual combination of high impact strength, transparency, and good electrical insulation properties. The properties of polycarbonate have led to many successful glazing applications, such as bus shelter, telephone booths, safety goggles, and lamp housings for automobiles. However, the poor wear and scratch properties of polycarbonate have limited its application in many fields. There have been many studies on improving the scratch and wear properties of polymer by applying coatings [1-4]. The DLC coatings have numerous useful properties such as transparency for visible and infrared light, high hardness and chemical inertness. They can be applied as a scratch-resistant coating. DLC coatings on a polycarbonate substrate maintained the high-speed impact strength [1]. Depositing DLC coating using a high frequency ion gun in this study made the polycarbonate surface wear-resistant and scratch-resistant. The effect of gas compositions and interlayer coating on deposited DLC coatings were characterized using a scanning electron microscope, Raman spectroscopy, ellipsometer, and microscratch tester. MATERIALS A proprietary acrylic polymer hard coating was applied to a Sam Yang TRIREX4 polycarbonate substrate with thickness of 1/8". The pencil hardness of polycarbonate and polymer hard coating were EE and 4H, respectively. The polymer hard coating was applied by dipping method and the coating thickness was about 10 jim. EXPERIMENTAL The DLC coatings were deposited on a polymer substrate with a hard coating by a direct ion beam gun with a 60 MHz: high-frequency ion beam source operated on a mixture of hydrogen 265
Mat. Res. Soc. Symp. Proc. Vol. 504 © 1998 Materials Research Society
and methane gases. The beam energy was 500 eV and ion current was 25 mA. The base pressure of vacuum chamber before deposition was 3 x 10-5 torr and it became 2.5 x 104 torr when reaction gases were introduced. The distance between ion gun source and the substrate was 22 cm. During deposition, the substrates were put on a rotating sample holder to have coating uniformity. Microscratch Tests The critical load for coa
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