Foldable OLED Bank Layer and Spacer Geometry for Crack Resistance
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Solution Overview
Problem
Organic light emitting display devices face issues with encapsulation layer cracking and separation of the organic light emitting diode during folding, leading to reduced impact resistance and affected display luminance due to lateral currents.
Innovation Solution
The device incorporates a substrate with a bank layer having a reverse tapered shape and spacers with tapered designs to minimize stress during folding, preventing separation and crack formation, and reducing lateral current effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional encapsulation layer structure is used in a foldable OLED device, then the device can be manufactured with standard processes, but the encapsulation layer cracks and the organic light emitting diode separates during folding
Solution Approach 1:
The patent changes the geometric parameters of the bank layer by forming it with a reverse tapered shape (wider at the top, narrower at the bottom). This parameter change allows the bank layer to better accommodate stress during folding, preventing cracks in the encapsulation layer and separation of the organic light emitting diode, thereby simultaneously improving both crack resistance and impact resistance
Solution Approach 2:
The patent employs a composite structure consisting of the bank layer, spacers, and encapsulation layer working together. The reverse tapered bank layer combined with tapered spacers creates a composite system that distributes stress more effectively, preventing cracking and separation while enhancing overall impact resistance
2Ease of manufacture
If the bank layer is made straight-sided, then the manufacturing process is simpler, but stress concentration occurs during folding causing encapsulation layer cracks
Solution Approach 1:
The bank layer is formed with a reverse tapered shape where the width varies along the height, creating a gradual transition rather than straight sides. This geometric parameter change reduces stress concentration during folding while remaining compatible with standard photolithography and etching processes, thus maintaining ease of manufacture while improving folding durability
3Device complexity
If spacers are not used or have flat tops, then the structure is simpler, but the organic light emitting layer separates from the panel during folding
Solution Approach 1:
The spacers are designed with tapered shapes that match the reverse tapered bank layer geometry. This parameter change in spacer geometry allows the organic light emitting layer to maintain proper adhesion to the panel during folding by distributing stress evenly, preventing separation while adding minimal structural complexity
Solution Approach 2:
The spacers exhibit asymmetric tapered shapes rather than symmetric flat-topped structures. This asymmetry allows the spacers to better conform to the stress distribution pattern during folding, improving layer adhesion and preventing separation while maintaining relatively simple device structure
Data Source
AI summary
An organic light emitting display device includes a substrate having a display area including a plurality of sub pixels and a non-display area which encloses the display area, a thin film transistor on the substrate, a planarization layer on the thin film transistor, an anode which is disposed on the planarization layer and is disposed for each sub pixel, a bank layer which is disposed on the planarization layer and includes a first opening unit exposing at least a part of the anode and a second opening unit spaced apart from the first opening unit, a first spacer on the bank layer, and a second spacer which is continuously disposed on the anode and the bank layer so as to overlap with a part of an edge of the first opening unit, and the bank layer has a reverse tapered shape and the second spacer has a tapered shape.