I am doing the research about printing OLED. The substrate is pixel-structured where polyimide is etched out to defined the RGB printing areas. Polyimide is not hydrophobic/oleophobic enough, and when ink-jet printing, if droplet is too large or the position is a bit drifted from the pixel pit, the doplet targeted for one pixel will have a chance to flow into the other nearby. I've heard that some people use some surface energy patterning treatment to make the pixel wall (i.e. polyimide) more hydrophobic/oleophobic while not disturbing the pixel pit (i.e. substrate electrode). How do they do this?
Yes, I've read some of their works. They spin-coat some hydrophobic molecule and uses photolithography to etch out the patterns. However my pixel substrate is already a pattern composed of hydrophobic polyimide (PI) and hydrophilic ITO surface (the area where PI is etched). Actually, it is a substrate that you use to fabricate OLED display where the etched areas define the RGB pixels. My intention is to further increase the hydrophobicity of the PI banks. So I don't think Sirringhaus's methods is useful here since one more etching for eliminating the coated molecules in the pixel areas is not feasible.
Dear Zhanhao, standard method is by using O2 plasma for wetting the ITO and CF4 plasma to make the polyimide non-wetting (while still have sufficient wetting of ITO). See for instance B.J. de Gans, P.C. Duineveld, U.S. Schubert, Advanced Materials, Vol. 16(2004), No. 3, p. 203-213 and references mentioned in this paper e.g. 31 and 27.
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