Flexible OLED Display Stress Distribution via Opening Flattening Films
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Solution Overview
Problem
Existing flexible organic light emitting diode (OLED) display devices are susceptible to damage from bending in the display region, as they do not account for stress distribution in this area, similar to the non-display region.
Innovation Solution
A display device configuration with a resin substrate and a light emitting element, featuring an opening in the inorganic insulating film of the TFT layer to expose the substrate, filled with an opening flattening film and covered by a metallic layer, which helps distribute stress and prevent damage during bending.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a flexible organic EL display device is designed with trenches only in the non-display region, then the light emitting element is protected from damage during bending in the non-display region, but the light emitting element remains vulnerable to damage during bending in the display region
Solution Approach 1:
The patent applies different structural configurations to different regions of the display device. In the non-display region, trenches are formed to protect against bending, while in the display region, a combination of opening portions, flattening films, and metallic layers is implemented. This local differentiation allows each region to have optimized protection mechanisms suitable for its specific functional requirements and bending characteristics.
Solution Approach 2:
The display device is segmented into distinct protective structures: opening portions penetrating the inorganic insulating film, flattening films filling these openings, and metallic layers covering the flattening films. This segmentation creates multiple discrete protective elements that work together to distribute and manage stress during bending in the display region, preventing concentration of stress at single points.
2Reliability
If the inorganic insulating film is made continuous to ensure electrical insulation, then electrical isolation is maintained, but stress concentration occurs during bending causing damage to the light emitting element
Solution Approach 1:
The inorganic insulating film is made discontinuous only at specific locations where opening portions are formed, while maintaining continuity in other areas. This localized discontinuity allows stress relief during bending without compromising the overall electrical insulation function of the film, as the openings are strategically positioned to minimize impact on insulation performance while maximizing stress distribution benefits.
Solution Approach 2:
The flattening film acts as an intermediary material that fills the opening portions and provides a transition zone between the rigid inorganic insulating film and the flexible underlying structures. This intermediary layer helps distribute stress during bending while maintaining the electrical insulation barrier, preventing direct stress concentration on the light emitting element.
3Strength
If opening portions are formed in the inorganic insulating film to relieve stress, then bending damage is prevented, but water intrusion pathways are created
Solution Approach 1:
The flattening film serves as an intermediary barrier that fills the opening portions, preventing direct exposure of the underlying structures to moisture. This intermediary layer maintains the protective function against water intrusion while still allowing the opening portions to fulfill their stress-relief function during bending.
Solution Approach 2:
The device employs a composite structure combining inorganic insulating film, organic flattening film, and metallic layers. This composite material approach creates multiple barriers with different properties: the inorganic film provides electrical insulation and chemical stability, the flattening film provides flexibility and moisture barrier properties, and the metallic layers provide additional mechanical strength and moisture protection, collectively preventing water intrusion through the opening portions.
Data Source
AI summary
In a display region of a display device, opening portions are formed in at least one layer of an inorganic insulating film making up a TFT layer in such a manner as to penetrate the inorganic insulating film to thereby expose an upper surface of a resin substrate, opening flattening films are provided in such a manner as to fill in the opening portions, and metallic layers are provided in such a manner as to cover upper surfaces of the opening flattening films.