Abstract
In the study using radio frequence (RF) plasma to modify the surface properties of polyester film, we observed that the variation trend in treatment effect was different between the two sides when used tetrafluoromethane as plasma gas. And the variation of surface hydrophilic and hydrophobic properties would reverse with treatment conditions. But this was not found when used nitrogen, oxygen, or argon as plasma gas. In this thesis, the further study used different plasma sources to establish the relationship between the CF4 plasma reactions and the varation of surface properties. Thus successfully develops the surface asymmetric modification and patterning technologies, and the hydrophilic and htdrophobic surface properties can be in-situ formed on polymer film surfaces, respectively. Whereas the water contact angle difference between different surfaces can be above 100 degree. In the study of using RF CF4 plasma to modify polyester films, we had observed the plasma glow had a relatively high intensity nearby the cathode. This represents had a relatively high particle density of active species of CF4 plasma nearby the cathode. The treated PET film surfaces had been characterized with X-ray photoelectron spectroscopy (XPS), contact angle measurements and atomic force microscopy. The analysis results showed that fluorine atoms were being grafted onto the surfaces, and the F/C ratios between the two sides were different. Besides, the O/C ratios also changed and were different between the two side surfaces, and both side surface roughness decreased. In literatures, the major reactive components of CF4 plasma are fluorine atomic radicals[57-60], and the vacuum ultraviolet irradiation may promote the reactions of fluorine-containing gas[45-46] or fluorine-containing gas plasma [64~65] to polymer materials. Therefore we propose that the surface asymmetric modification effect is mainly attributed to the asymmetric distribution of CF4 plasma atmosphere. Moreover, the fluorine atomic radicals and the irradiation of vacuum ultraviolet from plasma glow could be the key factors of the asymmetric surface modification. In the study of surface modification of polyimide films by microwave CF4 plasma downstream treatment, the results showed that treatment effects were similar to the RF plasma treatment. This reveals that the surface asymmetric modification technique doesn’t have the material and the equipment dependency. In the analyses of microwave CF4 plasma glow, the fluorine peak with the highest intensity shows at 703.3 nm. This reveals that the fluorine atoms are the major reactive species in CF4 plasma. And the relative peak intensities of fluorine atoms between the film and microwave window is higher than another side. This result points out that the CF4 plasma reactions are dominated by the fluorination reactions at polymer surface facing to the high fluorine atomic radical density atmosphere, and thus formed a high F/C ratio hydrophobic surface. In another side, the plasma reactions are dominated by etching reactions, and the resulting product polymer radicals, except the following chain scission or crosslinking reactions, would further react with atmosphere and oxidize to form oxygen-containing polar functional groups. In the study of surface patterning modification of polyimide films, CF4 microwave plasma treatment was carried on through a shadow mask. The surface property of masking region would gradually transform from hydrophobic to hydrophilic when the gap size is close to or below the calculated mean-free-path of fluorine atom. Therefore we can understand that the available fluorine atoms in the confined space between mask and polyimide film is limited and lower than the non-masking region, and thus resulting the hydrophilic and hydrophobic surfaces at masking and non-masking regions, respectively. Whereas the water contact angle difference between the two regions was above 100 degree. Followed by a typical electro-less plating process, Sn/Pd catalyst can be absorbed onto the hydrophilic region of the texturing polyimide film, and form copper circuits. In this study, CF4 plasma treatment was carried on through shadow mask and MgF2 lens, thus the effect of vacuum ultraviolet could be studied under the same particle density of fluorine atomic radicals. The results showed that the influence of vacuum ultraviolet irradiation is not remarkable to CF4 plasma reactions at polyimide film surfaces. And the particle density of fluorine atomic radicals in CF4 plasma atmosphere is the key factors for the asymmetric surface modification and patterning technologies.