Latest advances in substrates for flexible electronics

Recent advances in both organic- and inorganic-based electronics processed on flexible substrates offer substantial rewards in terms of being able to develop displays that are thinner, lighter, robust, and conformable, and can be rolled away when not required. In addition, plastic-based substrates coupled with the recent developments in solution deposition and ink-jet printing for laying down OLED materials and active-matrix thin-film-transistor (TFT) arrays open up the possibility of cost-effective processing in high volumes using roll to roll (R2R) processing.(1) To replace glass, however, a plastic substrate needs to be able to offer some or all of the properties of glass, i.e., clarity, dimensional stability, thermal stability, barrier, solvent resistance, and low coefficient of thermal expansion (CTE) coupled with a smooth surface. In addition, a conductive layer may be required. No plastic film offers all these properties so any plastic-based substrate will almost certainly be a multilayer composite structure.(1,2) This paper will discuss the issues associated with selecting plastic materials, contrast the various options, and highlight how to gain optimum performance through process control. This will be illustrated with examples of film in use in flexible electronic applications.