OLED Barrier Layer Segmentation for Moisture and Flexibility
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Solution Overview
Problem
Flexible OLED displays with plastic substrates face issues of high water vapor transmission rates and crack formation in barrier layers, leading to reduced flexibility and effectiveness in preventing moisture and oxygen ingress, which can cause product failure under stress.
Innovation Solution
A barrier layer comprising alternately stacked metal and insulation layers, with a buffer layer and a thin film encapsulation layer, is used to reduce water vapor transmission rates and prevent crack formation, ensuring flexibility and transparency while blocking moisture and oxygen.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a barrier layer is provided between the plastic substrate and the pixel circuit to prevent water transmission, then the water vapor transmission rate is reduced, but the barrier layer increases in thickness and flexibility deteriorates
Solution Approach 1:
The barrier layer is divided into multiple thin inorganic layers (SiOx, SiNx) stacked alternately with organic layers. This segmentation allows each layer to be thin and flexible while the combined structure provides superior water vapor transmission prevention through multiple barrier interfaces.
Solution Approach 2:
The barrier layer uses a composite structure combining inorganic materials (SiOx, SiNx) with organic materials. The inorganic layers provide low water vapor transmission rate while the organic layers provide flexibility, creating a composite barrier that achieves both protection and flexibility.
2Reliability
If the barrier layer is increased in thickness to assure predetermined WVTR level, then water vapor transmission prevention is improved, but cracks are readily formed under stress such as bending or torsion
Solution Approach 1:
The barrier layer is segmented into multiple thin alternating inorganic and organic layers. This segmentation prevents crack formation because each thin layer can flex independently under stress, and the organic layers act as crack arrestors between the brittle inorganic layers.
Solution Approach 2:
The organic layers are placed between the inorganic barrier layers to provide cushioning against stress. These organic layers absorb mechanical stress and prevent crack propagation in the brittle inorganic layers before cracks can form, maintaining integrity under bending or torsion stress.
3Ease of operation
If the barrier layer thickness is reduced to increase flexibility, then flexibility is improved, but the water vapor transmission prevention function deteriorates
Solution Approach 1:
The barrier layer combines inorganic materials (SiOx, SiNx) with organic materials in a multilayer composite structure. The inorganic layers provide low water vapor transmission rate despite thin thickness, while the organic layers maintain flexibility, achieving both low WVTR and high flexibility in a thin overall structure.
Solution Approach 2:
Instead of increasing thickness in one dimension to improve WVTR prevention, the solution uses multiple layers stacked in another dimension. The alternating inorganic and organic layers create multiple barrier interfaces that collectively provide superior WVTR prevention while maintaining thin overall thickness and flexibility.
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 effectively blocks moisture and oxygen ingress, preventing deterioration of the pixel circuit and organic light emitting diode, while maintaining excellent flexibility and transparency, even under bending or torsion stress.
Implementation Method 1
a barrier layer disposed on the flexible substrate... The barrier layer includes a plurality of metal layers and a plurality of insulation layers in which the metal layers and the insulation layers are alternatively stacked with each other on the flexible substrate
Implementation Method 2
The inorganic layers may include at least one selected from a group consisting of a silicon oxide (SiOx), a silicon nitride (SiNx), alumina (Al2O3), indium tin oxide (ITO), titanium oxide (TiO2), and gallium arsenide (GaAs), and may be formed using a plasma enhanced chemical vapor deposition (PECVD) method
Implementation Method 3
The barrier layer may further include a metal oxide layer formed at one side of one of the metal layers that contacts one of the inorganic layers. The metal oxide layer may be formed using an anodization method
Data Source
AI summary
An organic light emitting diode (OLED) display includes a flexible substrate, a barrier layer disposed on the flexible substrate, and an organic light emitting diode disposed on the barrier layer. The barrier layer includes a plurality of metal layers and a plurality of insulation layers in which the metal layers and the insulation layers are alternatively stacked with each other on the flexible substrate.