Pixel Electrode Adhesion via Composite IZO-Ag-ITO Layers
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Solution Overview
Problem
Current display devices with top-emission type organic light-emitting elements face challenges in achieving high reflectance and reliability due to the peeling of pixel electrodes, especially when using silver layers over insulating films with low adhesion, leading to defects and reduced yield.
Innovation Solution
A pixel electrode structure comprising a first conductive layer of indium-zinc oxide, a second conductive layer of silver, and a third conductive layer of indium-tin oxide, with specific thickness ratios and etching processes using oxalic acid and mixed acids to maintain adhesion and prevent peeling, is employed, along with a manufacturing method that forms these layers over an insulating film containing nitrogen, oxygen, and silicon.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a silver layer is used for high reflectance in the pixel electrode, then the reflectance is improved, but the adhesion to the insulating film deteriorates causing peeling
Solution Approach 1:
The pixel electrode uses a composite structure with multiple conductive layers (IZO, Ag, ITO, Al) instead of a single silver layer. This composite structure maintains high reflectance through the silver layer while the IZO and ITO layers provide adhesion to the insulating film, preventing peeling defects.
Solution Approach 2:
The IZO layer serves as an intermediary between the insulating film and the silver layer, providing adhesion while allowing the silver layer to maintain its high reflectance properties. The ITO and Al layers further mediate the connection between different functional layers.
2Ease of manufacture
If a simple pixel electrode structure is used, then the manufacturing process is simplified, but the adhesion and reliability deteriorate
Solution Approach 1:
The multi-layer conductive structure (IZO/Ag/ITO/Al) provides both improved adhesion and reflectance while maintaining compatibility with existing manufacturing processes. Each layer can be deposited using standard techniques, making the composite structure manufacturable despite its complexity.
3Productivity
If silver is deposited directly on the insulating film, then the manufacturing steps are reduced, but peeling occurs due to low adhesion
Solution Approach 1:
The IZO layer is deposited first as a preliminary adhesion layer before the silver layer is added. This preliminary action ensures that subsequent layers have proper adhesion to the insulating film, preventing peeling while maintaining an efficient manufacturing process.
Solution Approach 2:
The composite structure with IZO, Ag, ITO, and Al layers provides both adhesion and manufacturing efficiency. The layered composite can be deposited in a single manufacturing sequence, maintaining productivity while solving the peeling problem.
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 adhesion between the pixel electrode and insulating film, reduces peeling, and improves the reliability and yield of display devices by maintaining high reflectance and emission efficiency while minimizing defects.
Implementation Method 1
forming a first conductive layer including a conductive oxide containing indium and zinc; forming a second conductive layer over the first conductive layer, the second conductive layer containing silver; forming a third conductive layer over the second conductive layer
Implementation Method 2
etching the third conductive layer with oxalic acid using the resist as a mask
Implementation Method 3
etching the first conductive layer and the second conductive layer with an aqueous solution including nitric acid, acetic acid, and phosphoric acid
Implementation Method 4
a material with high reflectance is employed. For example, a pixel electrode including a metal with high reflectance to visible light, such as aluminum and silver
Data Source
AI summary
Disclosed is a display device having a pixel including a pixel electrode, an electroluminescence layer over the pixel electrode, and an opposing electrode over the electroluminescence layer. The pixel electrode possesses: a first conductive layer including a conductive oxide containing indium and zinc; a second conductive layer over the first conductive layer, the second conductive layer containing silver; and a third conductive layer over the second conductive layer, the third conductive layer including a conductive oxide containing indium and tin. A thickness of the first conductive layer is equal to or more than twice a thickness of the third conductive layer and equal to or less than five times the thickness of the third conductive layer.