OLED Groove Structure for Crack Confinement in Flexible Displays
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Solution Overview
Problem
The encapsulation structure of OLED displays in bent regions is prone to cracking due to the poor ductility of inorganic films, which can lead to damage and corrosion of metal traces when exposed to air, reducing the service life of the display.
Innovation Solution
A flexible substrate with a groove structure is used in the non-display region, covered by an inorganic film, to confine cracks and reduce stress during bending, while a laminated structure with deep holes and support pillars enhances flexibility and planarization, and the use of materials like silicon nitride or silicon oxide for the inorganic film provides a durable encapsulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the non-display region is made bendable to increase screen ratio, then the area of projection of non-display region is reduced, but the encapsulation structure is prone to cracking when bent
Solution Approach 1:
The non-display region is divided into multiple segments by forming groove structures that extend from the boundary line toward the bending direction. These grooves segment the continuous inorganic film into separate sections, allowing each segment to deform independently during bending without causing cracks to propagate across the entire encapsulation structure.
Solution Approach 2:
The groove structures are strategically positioned in the non-display region with specific geometric characteristics (inverted triangular cross-section, depth between one-third to two-thirds of substrate thickness). This creates local variations in film stress distribution, concentrating potential crack formation in the groove regions rather than in the display region, thereby preserving local integrity where it matters most.
2Reliability
If the inorganic film is used for encapsulation, then the organic layer is protected from air exposure, but the inorganic film generates cracks when bent due to poor ductility
Solution Approach 1:
The continuous inorganic film is segmented by groove structures into discrete sections. This segmentation allows the film to maintain its protective function while accommodating bending stresses through localized deformation at the groove sites, preventing catastrophic failure of the entire encapsulation layer.
Solution Approach 2:
The groove structures act as intermediary elements that mediate between the rigid inorganic film and the bending motion. By providing controlled sites for stress concentration and deformation, the grooves protect the overall encapsulation integrity while allowing necessary mechanical flexibility.
3Device complexity
If the organic layer is directly exposed to air, then the structure is simpler, but the metal traces are easily corroded by water and oxygen
Solution Approach 1:
Rather than using a completely different encapsulation approach, the patent segments the existing inorganic film structure to achieve both protection and flexibility. This maintains the proven effectiveness of inorganic encapsulation while adding geometric features that enable bending without compromising service life.
Data Source
AI summary
An organic light emitting diode (OLED) device and the method of fabricating thereof. The OLED device includes a substrate, a display region, a non-display region, and an encapsulation structure covering the display region and the non-display region. The non-display region is composed of a flexible substrate that is bendable, the flexible substrate is curved toward a second surface of the substrate. The non-display region is provided with at least one groove structure at an edge adjacent to the display region, the groove structure extends along a first direction which is parallel to a boundary line between the display region and the non-display region.