OLED Capping Layer Protects Second Electrode from Sealing Damage
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Solution Overview
Problem
The challenge in improving image quality and electrical characteristics of organic light-emitting display apparatuses is due to pollution or damage of the second electrode, often caused by sealing members or impurities, which affects the overall performance and reliability of these devices.
Innovation Solution
The implementation of a capping layer with a first and second capping layer, where the second capping layer is thinner and lighter-transmissive, and a third electrode with a weaker adhesive force to the capping layer, helps protect the second electrode and improve electrical characteristics and image quality by reducing surface resistance and preventing damage from external factors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sealing member is disposed on the second electrode to protect it, then the second electrode is protected from pollution and damage, but the sealing member itself causes pollution or damage to the second electrode
Solution Approach 1:
The patent introduces a capping layer as an intermediary component between the sealing member and the second electrode. This capping layer serves as a protective barrier that prevents the sealing member from directly contacting and damaging the second electrode, thereby resolving the contradiction where the sealing member both protects and damages the electrode
Solution Approach 2:
The protective structure is segmented into multiple functional layers: the sealing member for overall encapsulation, the capping layer for direct electrode protection, and the second electrode itself. This segmentation allows each layer to perform its specific function without interfering negatively with others
2Reliability
If the capping layer is made thicker to improve protection, then the second electrode is better protected, but the transparency and light emission are reduced
Solution Approach 1:
The patent optimizes the thickness parameter of the capping layer to achieve a balance between protection and transparency. By carefully controlling the thickness within a specific range, the capping layer provides adequate protection while maintaining sufficient light transmission for display functionality
Solution Approach 2:
The capping layer is designed with different properties in different regions: in the light emission area, it has optimized thickness for light output, while in the transmission area, it maintains transparency. This local quality differentiation allows simultaneous achievement of protection and optical performance
3Strength
If adhesive force between the third electrode and capping layer is increased to improve bonding, then the structural integrity is improved, but the manufacturing complexity and damage risk increase
Solution Approach 1:
The patent controls the adhesive force parameter within an optimal range rather than maximizing it. This moderate adhesive force is sufficient for structural integrity while avoiding excessive bonding that would complicate manufacturing and increase damage risk during assembly
Solution Approach 2:
The patent uses a standardized capping layer structure and material composition that can be replicated across different manufacturing batches. This standardization simplifies the manufacturing process by reducing variability and complexity in achieving the required adhesive properties
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 enhances the transparency and image quality of the organic light-emitting display apparatus by maintaining the integrity of the second electrode, reducing voltage drop, and simplifying the manufacturing process while maintaining high luminance and contrast.
Implementation Method 1
The intermediate layer includes an organic emissive layer, and when a voltage is applied to the first and second electrodes, the organic emissive layer produces visible rays
Implementation Method 2
a transmission area through which external light is transmitted
Data Source
AI summary
An organic light-emitting display apparatus including: a substrate; a plurality of pixels that are formed on the substrate and each have a light emission area from which visible rays are emitted and a transmission area through which external light is transmitted; a pixel circuit portion disposed in each light emission area of the plurality of pixels; a first electrode that is disposed in each light emission area and is electrically connected to the pixel circuit portion; an intermediate layer that is formed on the first electrode and includes an organic emissive layer; a second electrode formed on the intermediate layer; and a capping layer that is disposed on the second electrode and includes a first capping layer corresponding to the light emission area and a second capping layer corresponding to the transmission area. Accordingly, electrical characteristics and image quality of the organic light-emitting display apparatus may be improved.