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 μm to 70 μm 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.