Influence of C4F8 plasma treatment on size control of inkjet-printed dots on a flexible substrate

The paper aims to investigate the influence of C4F8 plasma treatment on the inkjet-printed dot sizes on flexible PI substrates using the response surface method. The whole experimental region of two independent variables was divided into a number of sub-domains to estimate the accurate relationship between the independent variables and the response. From the RSM analysis, desired dot diameters ranging from 30 mu m to 70 mu m could be obtained by selecting the proper combination of the RF power and gas pressure. The chemical and physical changes in plasma-treated surfaces were also characterized by contact angle measurements, scanning electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy. The results show that both RF power and gas pressure have a significant influence on the dot diameter. In some experimental region, well-defined dots cannot be produced due to unstable plasmas. The dot diameters on the plasma-treated surfaces are well correlated with the contact angles on them. The roughness and F/C ratio of surfaces are also affected by the plasma treatment. The plasma condition yielding higher F content results in more hydrophobic surfaces. (C) 2010 Elsevier B.V. All rights reserved