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

In this study, the effect of plasma surface treatments with C(4)F(8) and O(2) on inkjet-printed droplet sizes was investigated. The plasma processes were performed in two different ways: (1) sequential plasma treatment with C(4)F(8) followed by O(2) and (2) plasma treatment with C(4)F(8)/O(2) 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 O(2) 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 C(4)F(8)/O(2) gas mixture increase with raising the O(2) to C(4)F(8) 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 O(2). 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. (C) 2010 Elsevier B.V. All rights reserved.