OLED's barrier films and thin film encapsulation: IDTechEx's review: Page 3 of 6

July 25, 2019 //By Julien Happich
barrier film
Flexible and foldable high-performance barrier or encapsulation technology had long represented a technology challenge. The industry spent a decade and a half optimizing the approaches and the processes to achieve large-area production-grade results.

In displays, the film type has so far given way to conformal direct thin film encapsulation (TFE). Despite this, the developments on film type are still ongoing. There is engagement with other emerging markets which require barrier films. There are also improvements in face-seal adhesive technology (e.g., hot-melt type with embedded particles or others that can dramatically relax WVTR of the barrier itself with potentially significant beneficial consequences) and production processes including fully-solution processed techniques.

Even in terms of display markets, firms are taking the longer-view, hoping that they can (a) deliver a cost advantage (e.g., high web speeds, lowering yield requirements, etc) in the longer term for next-gen mother glass (substrate) sizes, and/or (b) offer a more accessible technology to new display producers who do not have the in-house know-how and/or the expensive equipment set to produce in-line TFE.

 

The incumbent: thin film encapsulation (TFE)

This approach is also based on a multi-layer structure principle. Indeed, it is essentially an evolution of the original Vitex approach. This approach is now commercialized on Gen6 production lines. In its current state, the inorganic SiNx layer is PECVD deposited at low temperature and the organic layer is inkjet printed and then cured. In previous generations, PVD and through-mask evaporation were used for the inorganic and organic layers, respectively. These transitions in production processes, as well as extensive optimization, have dramatically reduced layer numbers from 11 to 3, thus reducing equipment count, production steps, and overall TACT, whilst boosting flexibility and transparency. This is no easy feat especially as high yields must be maintained over a Gen6 mother substrate. This is critical because defects are expensive as they will waste the entire device including the TFT and OLED structure. The recent news about a Korean display maker having to suspend production on one of its Gen6 lines due to TFE quality further demonstrate the scale of this challenge.


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