Thin-Film Encapsulation Structure for Flexible Moisture-Barrier Displays
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Solution Overview
Problem
Display apparatuses face challenges in maintaining robustness against moisture penetration while achieving improved flexibility, especially when bent or folded, leading to potential failures due to stress-induced cracks in the encapsulation layers.
Innovation Solution
A display apparatus with a thin film encapsulation layer comprising a first encapsulation layer, a second encapsulation layer, and an organic encapsulation layer, where the second encapsulation layer includes alternately arranged inorganic and organic thin layers, with an elastic modulus of 5 GPa to 10 GPa, and the inorganic thin layers contact each other at the end, enhancing flexibility and reducing stress-induced cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick encapsulation layer is used to prevent moisture penetration, then moisture barrier performance is improved, but flexibility and bendability deteriorate
Solution Approach 1:
The encapsulation layer is divided into multiple thin inorganic layers (first, second, and third encapsulation layers) with an organic layer in between. This segmentation allows each layer to be thin and flexible while collectively providing strong moisture barrier performance, resolving the contradiction between thickness for barrier performance and thinness for flexibility.
Solution Approach 2:
The patent uses a composite structure combining inorganic encapsulation layers (providing moisture barrier) with an organic encapsulation layer (providing flexibility and stress relief). This composite approach allows the system to simultaneously achieve both moisture protection and mechanical flexibility, preventing stress-induced cracks during bending.
2Reliability
If a rigid encapsulation layer is used to protect against moisture, then barrier performance is improved, but stress-induced cracking increases during bending
Solution Approach 1:
The patent changes the elastic modulus parameter by introducing an organic encapsulation layer with lower stiffness between the inorganic layers. This parameter change allows the encapsulation structure to flex under stress without cracking, while the inorganic layers maintain their moisture barrier function.
Solution Approach 2:
The organic encapsulation layer acts as a cushioning layer that absorbs and distributes mechanical stress before it reaches the brittle inorganic encapsulation layers. This beforehand cushioning prevents stress concentration that would otherwise cause cracks in the moisture barrier layers during bending operations.
Data Source
AI summary
A display apparatus includes: a substrate including a display area and a peripheral area around the display area, the substrate having a bent portion; a plurality of display elements in the display area; and a thin film encapsulation layer over the plurality of display elements and including a first encapsulation layer, a second encapsulation layer over the first encapsulation layer, and an organic encapsulation layer between the first encapsulation layer and the second encapsulation layer, wherein the second encapsulation layer includes a plurality of inorganic thin layers and a plurality of organic thin layers alternately arranged, and a thickness of the second encapsulation layer is equal to or less than a thickness of the first encapsulation layer.