Unconventional, Laser Based OLED Material Direct Patterning and Transfer Methods

Abstract

Organic light emitting diode (OLED) displays have a number of desirable features such as high contrast and brightness, wide color range, thin structure and light weight, among others.(Hirano et al. 2007) OLED displays have several manufacturing requirements such as large area scalability and an increasing push towards smaller feature sizes, tighter feature shape control, high yield and low cost. However, traditional lithography and thermal evaporation deposition techniques have significant disadvantages, including the need for masks that are typically difficult to make to the required specifications at a reasonable price. The conventional vacuum deposition and photolithographic patterning methods are well developed for inorganic microelectronics. However, organic electronics materials are chemically incompatible with corrosive etchants, resists and developers used in conventional integrated circuit (IC) processing. In practice, conventional IC fabrication processes are subject to limitations, in that they are multi-step, involve high processing temperatures, toxic waste and are therefore expensive. Furthermore, the increasing size of electronic devices such as displays poses great difficulty in adapting standard microfabrication processes, including lithographic patterning. (Zschieschang et al. 2003, Ko et al. 2007) Therefore, there is a strong need to develop a novel process instead of complex modification of conventional vacuum deposition and photolithography based processes. OLED display manufacturing employs direct write techniques for patterning the various materials. Examples of OLED material direct write technologies include ink jet printing (Hashimoto et al, 2006, Gohda et al. 2002, Lee et al. 2002,, Kobayshi et al. 2002, Shirasaki et al. 2004, Fleuster et al. 2004, Lee et al. 2005, Saafir et al. 2005) screen printing (Shinar et al. 2007, Lee et al. 2009) and laser induced forward transfer (LIFT) (Hirano et al. 2007, Pique et al. 1999, Suh et al. 2003, Willis et al. 2005, Kyrkis et al. 2006). As described in a recent review on OLED RGB patterning, success of an OLED patterning scheme depends on the material type, device design, pixel array pattern, display format, substrate size, placement accuracy, process TACT-time, and defect density. The type of material and OLED architecture largely determine which type of RGB patterning can be applied. Other factors determining the