Foldable Display Encapsulation Structure for Moisture and Crack Resistance
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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 second encapsulation layer is thinner than the first, to reduce stress and prevent moisture penetration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-layer encapsulation structure is used, then the device complexity is low, but the resistance to moisture penetration and flexibility under bending conditions deteriorate
Solution Approach 1:
The patent applies composite materials by combining multiple inorganic encapsulation layers with an organic encapsulation layer in a multi-layered structure. The inorganic layers provide moisture barrier properties while the organic layer provides flexibility and stress accommodation, creating a composite encapsulation system that achieves both moisture resistance and bendability that single-layer structures cannot provide
Solution Approach 2:
The encapsulation layer is segmented into multiple functional layers: at least one inorganic encapsulation layer for moisture blocking and at least one organic encapsulation layer for flexibility. This segmentation allows each layer to perform its specific function optimally, with the inorganic layers handling moisture protection and the organic layer handling mechanical flexibility during bending
2Reliability
If a thick encapsulation layer is used, then the protection against moisture is improved, but the flexibility and resistance to cracking under bending deteriorate
Solution Approach 1:
The patent uses composite materials where thin inorganic encapsulation layers (providing moisture barrier) are combined with an organic encapsulation layer (providing flexibility). This composite approach allows achieving adequate moisture protection without requiring excessive thickness that would compromise flexibility, as each material contributes its strength in the appropriate functional area
Solution Approach 2:
Different regions of the encapsulation system have different qualities: the inorganic layers provide localized moisture blocking where needed, while the organic layer provides localized flexibility and stress absorption. This local quality differentiation allows the system to achieve both protection and flexibility without compromising either aspect
3Strength
If the encapsulation layer is made thinner, then the flexibility is improved, but the robustness against moisture penetration deteriorates
Solution Approach 1:
The patent employs composite materials where thin inorganic encapsulation layers are combined with an organic encapsulation layer. The inorganic layers, even when thin, provide effective moisture barriers due to their inherent low permeability, while the organic layer compensates for any potential defects and provides flexibility, achieving both thinness for flexibility and robustness for moisture protection
Solution Approach 2:
The encapsulation function is segmented between different material types: inorganic layers handle the moisture blocking function (even at thin thickness due to their low permeability), while the organic layer handles the flexibility function. This functional segmentation allows achieving both flexibility and moisture protection without requiring excessive thickness
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.