Photo-induced surface modification of polyimides for printable electronics fabrication

Manufacturing flexible electronic devices with printing technique is one of the key steps, but printing fine structure with ink jet technique is relatively limited, because positional precision of ink droplet deposition and the size of an ink droplet are not smaller than several microns. We prepared those polyimides whose surface wetability can be changed by photoirradiation, with which surface wetability can be photo-lithographically patterned to make channels and an ink droplet spread along the patterned area with photolithographic resolution. The degree of surface contact angle change of water on the polyimide is as large as 70° between before and after the photoirradiation. The mechanism is confirmed as the chemically amplified reaction of t-BOC group, and photochemical reaction of benzophenone moiety. Surface relief structure can be also patterned only by exposure without development with those polyimides containing PAG or PBG as additives. The mechanism is determined as the difference in the imidization temperature. Positive or negative tone of the relief can be controlled by the selection of the additives. Porous structure pattering with turbid/transparent structure can be also patterned by photoirradiation. Those polyimides are potentially high performance and functional materials for printable and flexible electronic devices.