Film Surface Treatment with O$_{\mathrm{2}}$/Ar Line Plasma under Atmospheric Pressure

Much attention has been given to application of non-thermal atmospheric pressure plasma (APP) to large-area surface treatment and development of a uniform and high-density large-scale APP device. So far, we have reported that a long-scale microwave APP (AP microwave line plasma: AP-MLP) with molecular gas is produced in a long slot on the waveguide wall by controlling electromagnetic power flow inside the waveguide to reduce standing waves. We reported spatially-uniform AP-MLP of \textasciitilde 100 cm in length using Ar or He and \textasciitilde 70 cm using N$_{\mathrm{2}}$ gas or O$_{\mathrm{2}}$/Ar admixture gas. In the case of \textasciitilde 0.1{\%} O$_{\mathrm{2}}$-admixed Ar, uniform O radical density of 1x10$^{\mathrm{13}}$ cm$^{\mathrm{-3}}$ in longitudinal length of 60 cm was observed. In this study, to demonstrate surface treatment processing, hydrophilic treatment of PET film surface is conducted using our plasma source with argon gas and its hydrophilicity and large-area spatial uniformity are evaluated. Furthermore, a few {\%} O$_{\mathrm{2}}$ is added to the argon microwave plasma and the film surface treatment is investigated. The hydrophilicity is improved in a relatively short time and the water contact angle is decreased with increasing the oxygen flow rate. The spatial uniformity of the processing is quite uniform in 20 cm.