Flexible OLED Encapsulation Structure for Fold-Stress Adhesion
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Solution Overview
Problem
Flexible OLED displays face issues with detachment of the organic light emitting layer due to repetitive folding, degradation from external moisture and air permeation, and reduced reliability due to compressive and tensile stresses.
Innovation Solution
The OLED device incorporates a substrate with a thin film transistor, an inter-layered insulating layer, an overcoat layer, a first electrode, a bank, an organic light emitting layer, and a protection film, featuring specific hole locations in the overcoat layer, bank, and protection film to relieve stress and prevent detachment, while using inorganic and organic encapsulation layers to block moisture and air.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the flexible OLED display is repeatedly folded to achieve portability and flexibility, then the device can be folded and stored compactly, but the organic light emitting layer may detach and reliability degrades
Solution Approach 1:
The device is divided into flexible and rigid regions, with the flexible substrate containing the organic light emitting layer and electrodes, and the rigid cover lens and touch sensor layers providing structural support. This segmentation allows the organic layer to be protected from stress while maintaining overall flexibility.
Solution Approach 2:
A buffer layer is introduced between the flexible substrate and the rigid cover lens to absorb and distribute mechanical stress during folding. This buffer layer prevents stress concentration that would otherwise cause the organic light emitting layer to detach, providing protective cushioning before damage occurs.
2Length of stationary object
If the flexible OLED display is made ultra-thin to reduce device thickness, then the profile becomes thinner and lighter, but the device becomes more susceptible to damage from repetitive stress
Solution Approach 1:
The device employs a composite structure combining flexible materials (plastic substrate, organic layers) with rigid materials (glass or plastic cover lens, inorganic encapsulation layers). This composite design achieves ultra-thin profile while the rigid components provide necessary mechanical strength and stress resistance.
Solution Approach 2:
The device uses thin-film encapsulation with multiple alternating inorganic and organic layers that provide both mechanical strength and flexibility. The inorganic layers (e.g., SiOx, SiNx) provide barrier properties and structural support, while the organic layers provide flexibility and stress absorption, enabling ultra-thin design with maintained strength.
3Adaptability or versatility
If the flexible OLED display uses a plastic substrate instead of glass to enable bending, then the device becomes flexible and portable, but the organic light emitting layer may detach due to stress
Solution Approach 1:
Different regions of the device have different mechanical properties: the substrate and organic layers are designed to be flexible to enable bending, while the cover lens and encapsulation layers provide localized rigidity and stress distribution. This local quality differentiation allows bendability while maintaining layer stability through strategic placement of rigid support elements.
4Reliability
If the flexible OLED display is designed with protective layers to prevent moisture and air permeation, then the lifetime is extended, but the device thickness increases
Solution Approach 1:
The device uses thin-film encapsulation with multiple alternating inorganic and organic layers that provide both mechanical strength and flexibility. The inorganic layers (e.g., SiOx, SiNx) provide barrier properties and structural support, while the organic layers provide flexibility and stress absorption, enabling ultra-thin design with maintained strength.
Solution Approach 2:
The device employs a composite structure combining flexible materials (plastic substrate, organic layers) with rigid materials (glass or plastic cover lens, inorganic encapsulation layers). This composite design achieves ultra-thin profile while the rigid components provide necessary mechanical strength and stress resistance.
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 solution enhances the reliability and adhesion of the organic light emitting layer, minimizes device thickness, and prevents impurity permeation, thereby improving the durability and performance of flexible OLED devices.
Implementation Method 1
an organic light emitting layer on the first electrode
Data Source
AI summary
An inorganic light emitting diode device includes: a substrate including a plurality of sub-pixels; a thin film transistor (TFT) in each of the plurality of sub-pixels, wherein the TFT has at least one inorganic layer; an encapsulation layer on an organic light emitting layer, wherein the encapsulation layer includes at least one organic encapsulation layer and at least one inorganic encapsulation layer; and an opening exposing the inorganic layer of the TFT, wherein the opening connects the at least one inorganic encapsulation layer with the inorganic layer of the TFT.