Friday, July 2, 2021

Future foldable and flexible Display with NCD’s ALD encapsulation technology

In the global market of smart phones, competition on mobile’s form factors has been an important issue since foldable smart phones had launched following cured ones. Samsung electronics applied in-folding form factor to Galaxy Fold and Galaxy Z Flip, and Huawei used out-folding form factor to Mate X. New two or three folding form factor has been unveiling to the public beyond in-folding and out folding displays.

Flexible displays consist of Thin Film Transistor (TFT), Organic Light Emission Diode (OLED) and multi encapsulation layers. Generally organic and inorganic laminated layers is used for foldable displays and PECVD has applied to deposit inorganic materials.

Basically, Inorganic layers is lack of brittleness then their encapsulation property is degraded with continuous mechanical stress. ALD method for TFE was considered instead of PECVD due to their excellent encapsulation characteristics with thicknesses of few tens of nanometers. The reliability of the tool blocked applying to production at that time.

But because of the superior encapsulation property using ALD, many universities, institutes as well as display companies have been developing ALD inorganic layers for flexible displays and evaluating hundreds of thousand times folding test considering actual use recently.

LucidaTM GD Series ALD

The customer which has NCD’s Lucida GD Series ALD, measured folding test on flexible displays with inorganic layers using ALD instead of using PECVD and showed great performance under actual display operation. The 5.85 inch AMOLED display panels for in-folding and out-folding consisted of encapsulation structure of 30nm Al2O3 ALD/ 8㎛-Polymer/ 30nm Al2O3 and was tested in-folding and out-folding evaluation of 200,000 times with bending radius of 2R under light status after the 1st reliability test of RA 60℃/90% for 500hr. There were no dark spots on the panels after finishing the folding measurement. The 2nd reliability test of RA 60℃/90% for 48hr followed folding evaluation and then the TFE status was examined without any cracks.

Using NCD’s large area batch ALD system for foldable phones could obtain superior encapsulation property and flexibility with very thin inorganic layers to current ones using PECVD as well as provide great productivity because the batch tool can process lots of panels at one time.

Then NCD really looks forward to applying its large area batch ALD technology to encapsulation of future flexible display with in/out-folding and very small bending radius because of having solved the previous issues without both reliability and productivity that the reason is why ALD equipment didn’t apply for mass production of flexible display.

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