OLED Thin-Film Encapsulation Crack-Stopper Design
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Solution Overview
Problem
Inorganic dielectric layers in thin-film encapsulation of organic light-emitting diode displays are prone to cracking when display panels are cut from a common substrate, leading to potential damage and the need for larger inactive border areas due to the requirement for precise shadow mask accuracy.
Innovation Solution
A peripheral crack-stopper structure comprising parallel inorganic lines and an overlapping organic layer is implemented along the edge of the display, which reduces the risk of cracking and delamination by creating weaker areas in the dielectric layers, thereby minimizing the inactive border size and relaxing the accuracy demands on chemical vapor deposition shadow masks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If chemical vapor deposition shadow masks are used to block inorganic dielectric deposition around the periphery of each display panel, then cracking of inorganic dielectric is prevented and bond pads are protected, but shadow mask accuracy requirements increase and inactive border areas become larger than desired
Solution Approach 1:
The patent applies preliminary action by forming crack-stopper structures (discontinuous organic layers) in the inactive border area before the final encapsulation layers are deposited. These pre-formed structures create intentional weak points that guide crack propagation away from the active display area and bond pads, thereby preventing cracking without requiring precise shadow mask alignment during subsequent deposition processes.
2Reliability
If chemical vapor deposition shadow masks are used to block inorganic dielectric deposition around the periphery of each display panel, then cracking of inorganic dielectric is prevented, but inactive border areas become larger than desired
Solution Approach 1:
The patent applies local quality by creating discontinuous organic layer structures specifically in the inactive border region, rather than applying a continuous encapsulation layer across the entire panel. This localized approach provides crack-stopping functionality where needed (at the periphery) while minimizing the extent of the inactive border area, allowing the active display area to be maximized.
3Reliability
If inorganic dielectric layers are used in thin-film encapsulation, then pixel protection from environmental exposure is provided, but cracking occurs when display panels are cut from the common substrate
Solution Approach 1:
The patent applies composite materials by combining inorganic dielectric layers with organic layer structures to form a multi-layer encapsulation system. The inorganic layers provide environmental protection (moisture and oxygen barrier), while the organic crack-stopper structures provide crack resistance by creating intentional weak points that arrest crack propagation. This composite structure achieves both protection functions simultaneously.
Solution Approach 2:
The patent applies segmentation by forming discontinuous (non-continuous) organic layers within the encapsulation structure. These segmented organic layers create multiple small crack-stopping barriers distributed across the inactive border area, which effectively arrest crack propagation while allowing the overall encapsulation structure to remain intact and protective.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The crack-stopper structure effectively prevents crack propagation and delamination, reducing the risk of damage to the display and minimizing inactive border areas, while also reducing the complexity and accuracy requirements for shadow mask alignment during chemical vapor deposition.
Implementation Method 1
A strip of the organic layer may overlap the parallel inorganic dielectric lines and may run parallel to the edge of the display. The crack-stopper structures may have parallel polymer lines.
Implementation Method 2
A thin-film encapsulation layer is used to protect the pixels from damage due to environmental exposure. The thin-film encapsulation layer includes inorganic dielectric.
Implementation Method 3
Following fabrication, individual display panels can be cut from the common substrate using a laser.
Data Source
AI summary
A display may have organic light-emitting diode pixels formed from thin-film circuitry. An organic layer including planarization layers and a pixel definition layer may overlap the thin-film circuitry. Thin-film encapsulation may overlap the organic layer. The thin-film encapsulation may be formed from an organic dielectric layer interposed between two layers of inorganic dielectric material. A strip of peripheral crack-stopper structures may run along an edge of the display and may surround the array of pixels. The crack-stopper structures may include parallel inorganic lines formed from a first inorganic layer such as an inorganic layer of the thin-film circuitry. A strip of the organic layer may overlap the parallel inorganic lines. The crack-stopper structures may have parallel tapered polymer lines. The polymer lines may be overlapped by a second inorganic dielectric layer formed from the inorganic material of the thin-film encapsulation layer.