ITO-Al-MoW Layered Electrode for Display Reflectivity and Resistance
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Solution Overview
Problem
In top emission-type active matrix organic EL display devices, the surface roughness caused by hillocks during etching of pixel electrode banks leads to unstable hole injection, and conventional layered wiring structures fail to maintain high reflectivity while reducing wiring resistance, which shortens the device's useful life.
Innovation Solution
A layered structure of ITO2/Al/MoW/ITO1 is used, where ITO1 and ITO2 are directly connected, and the widths of the layers are optimized to minimize contact with the resist stripping liquid, allowing Al/MoW to function as auxiliary wiring and maintaining electrical continuity without lowering reflectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional layered wiring structure (silicon-type inter-layer insulating film between reflective film and pixel electrodes) is used to prevent battery reactions, then reliability is improved, but device complexity and manufacturing process length increase
Solution Approach 1:
The patent removes the silicon-type inter-layer insulating film from the conventional layered structure. Instead of using multiple layers (reflective film + silicon insulating film + pixel electrodes), the invention directly connects the reflective film (Al/MoW) with the pixel electrodes (ITO), extracting the unnecessary insulating layer while maintaining reliability through optimized layer width design that prevents battery reactions.
Solution Approach 2:
The patent segments the reflective film into a layered structure of Al/MoW with specific width relationships. The intermediate layer (Al) and upper-layer (MoW) are designed with controlled widths where the upper-layer width is 0.5-2.0 times the intermediate layer width, creating functional segments that prevent battery reactions while maintaining simplicity.
2Ease of manufacture
If the aluminum of the pixel electrodes is stripped away during etching, then manufacturing is simplified, but surface roughness increases and hole injection stability deteriorates
Solution Approach 1:
The patent uses a composite material structure for the reflective film consisting of Al/MoW layers. This composite structure allows the aluminum to be effectively stripped during etching while the MoW layer remains to provide a smooth surface, combining the manufacturing benefits of aluminum etching with the surface quality benefits of molybdenum-tungsten.
3Reliability
If auxiliary wiring is added to reduce common electrode resistance, then electrical performance is improved, but device complexity and manufacturing steps increase
Solution Approach 1:
The patent makes the reflective film structure serve dual functions: as the reflective layer and as the auxiliary wiring for the common electrode. The Al/MoW layered structure with specific width ratios provides both optical reflection and electrical conduction functions, eliminating the need for separate auxiliary wiring layers and reducing overall device complexity.
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 structure achieves high reflectivity and reduced wiring resistance, enhancing the operational efficiency and lifespan of the display device by preventing battery reactions and ensuring stable current injection.
Implementation Method 1
ITO1 and ITO2 are directly connected, and the widths of the layers are optimized to minimize contact with the resist stripping liquid, allowing Al/MoW to function as auxiliary wiring and maintaining electrical continuity
Implementation Method 2
A layered structure of ITO2/Al/MoW/ITO1 is used, where ITO1 and ITO2 are directly connected, and the widths of the layers are optimized to minimize contact with the resist stripping liquid, allowing Al/MoW to function as auxiliary wiring and maintaining electrical continuity without lowering reflectivity
Implementation Method 3
An Al/molybdenum-tungsten alloy (MoW) formed by sputtering is formed into a reflective film by wet bulk etching
Data Source
AI summary
There is provided a display device comprising a plurality of active elements on a substrate, a first insulating film for covering the active elements, electroconductive films were separated for each pixel on the first insulating film, a light-emitting layer disposed in an upper layer of the electroconductive films, and a common electrode disposed in an upper layer of the light-emitting layer, wherein a structure is used in which the electroconductive films have a layered film of a first electroconductive film, second electroconductive film, and third electroconductive film; the first electroconductive film is composed of ITO or chromium; the second electroconductive film is composed of aluminum with alumina on a surface; the second electroconductive film covers outside edges of the first electroconductive film; the third electroconductive film is composed of ITO; and the first electroconductive film and third electroconductive film are caused to contact each other.