OLED Thin Film Encapsulation Structure for Moisture Resistance
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Solution Overview
Problem
The existing thin film encapsulation structures for OLED display devices lack sufficient moisture-resistant reliability and mass-productivity due to the limitations of forming organic barrier layers using printing methods, which result in incomplete coverage and reduced bendability.
Innovation Solution
A thin film encapsulation structure is developed with a relatively thin organic barrier layer, where the organic flattening layer is formed on an inorganic protective layer, and the organic EL element layer is covered by a first and second inorganic barrier layer, with the organic barrier layer being enclosed by the inorganic barrier layer joint portion, and the tapering angle of the side surface of the first inorganic barrier layer is less than 90 degrees, enhancing moisture resistance and productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a relatively thick organic barrier layer (5-20 μm) is used to provide sufficient moisture barrier property and flatten the element substrate surface, then moisture-resistant reliability is improved, but bendability of the OLED display device is limited
Solution Approach 1:
The encapsulation structure is segmented into multiple thin inorganic barrier layers (first and second inorganic barrier layers) alternating with thin organic barrier layers, replacing a single thick organic barrier layer. This segmentation provides sufficient moisture barrier property through the stacked inorganic layers while maintaining flexibility with thinner organic layers.
Solution Approach 2:
The encapsulation structure uses a composite of inorganic and organic barrier layers stacked alternately. The inorganic layers provide superior moisture barrier properties, while the thin organic layers provide flattening function and flexibility, creating a composite structure that balances both requirements.
2Reliability
If a relatively thick organic barrier layer is formed by printing technology (inkjet method, microjet method) in air or nitrogen atmosphere, then surface flattening and moisture barrier are achieved, but mass-productivity is low due to repeated vacuum chamber operations
Solution Approach 1:
The formation processes of inorganic and organic barrier layers are merged into a single continuous vacuum operation. Both types of layers are formed sequentially within the vacuum chamber without breaking vacuum, eliminating repeated vacuum chamber operations and significantly improving mass-productivity.
Solution Approach 2:
The film formation process operates continuously in vacuum without interruption. The inorganic barrier layer is formed first, followed by the organic barrier layer, with both processes occurring in continuous sequence within the vacuum chamber, maintaining continuous useful action and improving productivity.
3Ease of manufacture
If printing technology is used to form the organic barrier layer, then the process can be performed in air or nitrogen atmosphere, but incomplete coverage and insufficient moisture barrier property result
Solution Approach 1:
The mechanical printing process is replaced with vapor-phase deposition in vacuum. The organic barrier layer material is supplied as vapor or mist in vacuum atmosphere, allowing uniform coating and complete coverage through vapor condensation, eliminating the incomplete coverage issue of printing methods.
Solution Approach 2:
The formation process uses vacuum atmosphere as an inert environment, replacing air or nitrogen atmosphere. This vacuum environment enables complete and uniform coverage of the organic barrier layer through vapor-phase deposition, ensuring sufficient moisture barrier property while maintaining process simplicity.
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
This configuration improves the moisture-resistant reliability and mass-productivity of OLED display devices by ensuring complete coverage and reducing water vapor ingress, while maintaining flexibility and efficient production processes.
Implementation Method 1
the inorganic barrier layer is formed by a thin film formation technology in a vacuum atmosphere (e.g., less than, or equal to, 1 Pa)
Implementation Method 2
An organic material heated and gasified to be mist-like is supplied onto an element substrate maintained at a temperature lower than, or equal to, room temperature
Implementation Method 3
The organic material in drops moves on the substrate by a capillary action or a surface tension to be present locally, namely, at a border between a side surface of the protruding portion and a surface of the element substrate
Implementation Method 4
Then, the organic material is cured to form the first resin member at the border
Data Source
AI summary
An organic electroluminescent device includes a substrate, driving circuit layer, inorganic protective layer, organic flattening layer, organic electroluminescent element layer, and TFE structure. The TFE structure includes a first inorganic barrier layer, organic barrier layer, and second inorganic barrier layer. The organic flattening layer is formed in a region where the inorganic protective layer is formed, organic electroluminescent elements are located in a region where the organic flattening layer is formed, and an outer perimeter of the TFE structure crosses lead wires and is present between an outer perimeter of the organic flattening layer and an outer perimeter of the inorganic protective layer. In a region where the inorganic protective layer and the first inorganic barrier layer are in direct contact with each other on the lead wires, a tapering angle of a side surface of a cross-section of the first inorganic barrier layer is smaller than 90 degrees.