Absorption layers of ink vehicles for inkjet-printed lines with low electrical resistance

Low concentrations of metallic nanoparticle inks often produce a coffee-ring effect, thereby resulting in high electrical resistance in inkjet-printed lines. The coffee-ring effect is due to a convection flow of ink droplets and can be overcome by reducing the flow. Here we report the formation of absorption layers of ink vehicles on pristine polyimide films and fabrication of convex-shaped lines without the coffee-ring effect even if a low concentration of commercially available ink is used. The coated layers increased the ink concentration and prevented a convection flow of ink droplets. As a result, the electrical resistance of the inkjet-printed lines on polymer-coated polyimide films (8 Omega) was improved threefold over that of lines printed on pristine polyimide films (24 Omega). This is a similar improvement to inkjet-printed lines that were heated gradually (7 Omega), which is one of the methods that can reduce convection flow. Durability tests were conducted and electrical resistance was measured on inkjet-printed lines on polymer-coated polyimide films. Even under harsh environments, the lines showed excellent electrical performance, and they can easily be integrated into practical applications.