| Protection from oxygen and moisture is crucial for organic electronics used in flexible display applications. When polymeric substrates are employed in flexible display applications, a barrier layer is required to protect the enclosed functional materials and layers from oxygen and water vapor permeation. In this study, barrier coatings consisting of organic and inorganic films were developed for the polymeric substrate to ensure sufficient protection. We have explored aqueous solution processing to deposit oxide films on the organic substrate. In this study, polyethylene terephthalate (PET) commonly used for an organic substrate, are coated with SiO2 and TiO 2 films. Importantly, the oxides coating is a solution-based process at very low temperatures, 70°C and 50°C for SiO2 and TiO 2, respectively. So the substrate can avoid premature failure due to high process temperature, and is applicable to organic structures, cheap and environment friendly. The modification of oxide coatings with UV/ozone induced SiO2 formation from polysiloxane organic "defect-healing" layer resulted in combined improvement of water vapor barrier (WVTR=8.3→3.8g/m 2/day) and critical failure strain (COS=0.7→1.6%) of barrier films. The present work also investigates the mechanical integrity of barrier films developed for flexible displays. Interfacial adhesion and mechanical properties of the resultant coatings were characterized by nano-indentation and fragmentation test, and bending test. The progressive failure of the thin coating can be examined in situ in an optical microscope by fragmentation test. The cohesive strength of the barrier coatings of SiO2 and TiO2 were 0.27 and 0.36 GPa, respectively. And the adhesive property was also analyzed in terms of work of adhesion, 31.4 and 57.9 mJ/m2 for SiO2 and TiO2, respectively. |
