Effects of N2 addition on enhanced scratch resistance of flexible polycarbonate substrates by low temperature plasma-polymerized organo-silicon oxynitride

An investigation was conducted on enhanced scratch resistance of polycarbonate (PC) substrates by low temperature plasma-polymerized organo-silicon oxynitride (SiO_xC_yN_z) with various N₂ flow rates. It was found that the low temperature plasma-polymerized SiO_xC_yN_z with tetramethylsilane (TMS)-O₂-N₂ plasmas in room temperature (23 °C) can be used for improving the scratch resistance of PC substrates. Scratch test demonstrates this improvement. The scratch resistance of PC substrates was greatly enhanced from the overwhelming presence of scratching (90%) on un-treated PC substrates to a complete lack of scratching (0%) on TMS-O₂-N₂ plasma-polymerized PC substrates with steel wool for 200 cycles at 300 g loading. The results of this study indicate the performance of scratch resistance on PC substrates was highly dependent on the surface characteristics of PC substrates. The hardness of PC substrates was determined by the pencil test. The surface morphology of PC substrate was monitored by atomic force microscopy (AFM) and field emitted scanning electron microscopy (FESEM). The atomic compositions and chemical bondings of TMS-O₂-N₂ plasma-polymerized SiO_xC_yN_z were analyzed by X-ray photoelectron spectroscopy (XPS).