Optimization of multilayer inorganic/organic thin film structure for foldable barrier films

Abstract

Currently, the paradigm of display market is changing from rigid display to flexible display. The ultimate goal of flexible display is to implement a freely foldable display. OLEDs have attracted much attention as a suitable display device for realizing a flexible and transparent display. However, one of the biggest problems of OLED devices is that the organic materials of OLEDs are very sensitive to oxygen and moisture, and therefore the devices are deteriorated by a small amount of moisture. Therefore, the development of a flexible thin film moisture barrier film is considered to be an important issue in improving the lifetime of flexible OLEDs. In fabricating flexible moisture barrier films that are essential for future flexible OLEDs, organic / inorganic multilayer structures are an essential structure for achieving low WVTR and high flexibility. In general, inorganic materials have excellent barrier properties, but are disadvantageous in that they are very vulnerable to mechanical deformation. Organic materials have low barrier properties but have a strong resistance to mechanical deformation. Therefore, in this study, we tried to maximize the moisture barrier property by substituting organic material with organic/inorganic hybrid material which has relatively good barrier property and strong resistance to mechanical deformation and by depositing inorganic material using atomic layer deposition. In order to achieve excellent moisture barrier properties, the use of inorganic materials is inevitable. In this study, we sought to improve the flexibility of moisture barrier films by investigating the structure minimizing mechanical deformation on brittle inorganic materials by using FEA simulation. The structure of the 1 dyad, 2 dyad moisture barrier film with the neutral plane as close as possible to the alumina layer was designed and experimentally verified. Finally, the moisture permeability of the film was measured, and it was confirmed that the film designed by FEA had a stable moisture barrier property even after folding test of 1,000 and 10,000 times. These experimental results demonstrate that the experimental design by FEA for moisture barrier films can be applied to the fabrication of moisture film barrier films in practice. In the future, it will be possible to design a structure optimized for folding through the simulation method applied in this study for the design of a flexible moisture barrier film.