Effects of plasma surface treatments on inkjet-printed feature sizes and surface characteristics

Abstract

In this study, the effect of plasma surface treatments with C4F8 and O2 on inkjet-printed droplet sizes was investigated. The plasma processes were performed in two different ways: (1) sequential plasma treatment with C4F8 followed by O2 and (2) plasma treatment with C4F8/O2 gas mixture. The plasma-treated surfaces were characterized by contact angle measurement, field emission scanning electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy. For the sequentially plasma-treated surfaces, additional O2 plasma treatment makes the surface more hydrophilic, leading to a larger droplet diameter as a result of surface etching. The diameters of the droplets on the surfaces plasma-treated with C4F8/O2 gas mixture increase with raising the O2 to C4F8 volume ratio up to 0.4; however, they tend to decrease at the volume ratio of 0.6 and then increase again with further addition of O2. Measured contact angles are in good agreement with the variation of droplet diameters. The tendency of variation in morphology and F/C ratio of treated surfaces are also different depending on the plasma treatment process. The combined effects of F/C ratio and surface morphology play a major role in determining the surface wettability.