Surface Treatment of Polymer Film by Atmospheric Pulsed Microplasma: Study on Gas Humidity Effect for Improving the Hydrophilic Property

Surface treatment of a poly(ethylene naphthalate) (PEN) film by atmospheric pulsed microplasma with humid Ar gas was experimentally investigated. A Marx generator with metal–oxide–semiconductor field-effect transistor (MOSFET) switches that generates negative pulses was used for generating microplasma. Hydrophilization was estimated by measuring contact angle before and after the microplasma surface treatment by a remote process. The initial contact angle was about 76°. The minimum contact angle of about 20° was obtained after a treatment, a discharge voltage of -1.3 kV negative pulse, a frequency of 24 kHz, a gas relative humidity of about 60%. Analysis by X-ray photoelectron spectroscopy (XPS) showed a decrease in the C 1s peak corresponding to the C–H bond or C–C bond, and increases in the O 1s peaks corresponding to the C=O bond or O–H bond.