Display Electrode Layout to Prevent Galvanic Dark Spots
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Solution Overview
Problem
Display devices face issues with dark spot defects and short-circuit defects due to galvanic reactions between conductive layers and wiring, especially when standard reduction potentials of materials in the conductive layer and wiring differ significantly.
Innovation Solution
A dummy pattern made of the same material as the pixel electrode is formed to cover the sidewall of the power supply line, preventing galvanic reactions by ensuring that silver ions generated during pixel electrode formation do not react with aluminum atoms in the power supply line.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conductive layer is formed and etched to form electrodes and wiring, then the display device can be manufactured with standard processes, but galvanic reactions occur between the conductive layer and wiring when materials have different standard reduction potentials, causing dark spot defects and short-circuit defects
Solution Approach 1:
An insulating layer is introduced as an intermediary between the conductive layer (pixel electrode) and the wiring (power supply line). This insulating layer prevents direct contact between the two conductive materials, thereby eliminating the galvanic reaction pathway while allowing both layers to coexist in the same device structure. The insulating layer acts as a mediator that maintains electrical isolation between components that would otherwise react chemically.
Solution Approach 2:
The device structure is segmented into distinct functional layers with clear boundaries. The conductive layer, insulating layer, and wiring are separated into different vertical and horizontal zones. This segmentation prevents unwanted interactions between layers with different materials, allowing each layer to perform its intended function without causing galvanic reactions with adjacent layers.
2Reliability
If the insulating layer completely covers the power supply line, then galvanic reactions are prevented, but the manufacturing process becomes more complex and time-consuming
Solution Approach 1:
The insulating layer is applied selectively rather than uniformly across the entire substrate. It is positioned specifically at regions where galvanic reactions are most likely to occur - namely where the conductive layer and power supply line are in close proximity or make contact. This localized application of the insulating layer provides defect prevention exactly where needed, while minimizing the additional manufacturing steps and time required.
Solution Approach 2:
Rather than completely covering the entire power supply line with the insulating layer, the solution applies the insulating layer partially - only at the critical sections where galvanic reactions pose a risk. This partial action approach provides sufficient protection against defects while avoiding the excessive manufacturing complexity and time that would result from complete coverage of all power supply line regions.
3Reliability
If additional protective layers are added to prevent galvanic reactions, then defect prevention improves, but device complexity and manufacturing costs increase
Solution Approach 1:
The insulating layer is designed to serve multiple functions simultaneously: it provides electrical insulation to prevent galvanic reactions, maintains structural integrity of the device, and can be integrated with existing manufacturing processes. By making the insulating layer multi-functional, the patent avoids adding specialized protective structures that would increase device complexity, instead utilizing a versatile layer that accomplishes multiple protective and structural roles.
Solution Approach 2:
The insulating layer is merged with the existing device architecture rather than being added as a separate, standalone protective component. It is integrated into the layer structure along with the conductive layer and wiring, forming a unified multi-layer device structure. This merging approach prevents galvanic reactions without significantly increasing overall device complexity, as the insulating layer becomes an inherent part of the device's structural design rather than an additional protective add-on.
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 implementation of the dummy pattern effectively prevents dark spot defects and short-circuit defects, while also reducing manufacturing time and costs by allowing the dummy pattern and pixel electrode to be formed simultaneously.
Implementation Method 1
The galvanic reaction is an electrochemical process in which a metal ion is reduced based on oxidation-reduction reactions when two metals having different standard reduction potentials from each other are connected by the electrolyte. The galvanic reaction may occur when standard reduction potentials of materials included in the conductive layer and the wiring are relatively greatly different.
Data Source
AI summary
A display device includes a substrate having a display area and a peripheral area, a pixel disposed on the substrate in the display area, the pixel including a pixel circuit, a pixel electrode electrically connected to the pixel circuit, an emission layer disposed on the pixel electrode, and an opposite electrode disposed on the emission layer, a power supply line disposed on the substrate in the peripheral area, the power supply line for supplying a power voltage to the pixel, an insulating layer covering the pixel circuit and the power supply line, the insulating layer including an opening exposing at least a portion of the power supply line, and a dummy pattern including a same material as the pixel electrode, the dummy pattern covering a sidewall of the power supply line exposed by the opening of the insulating layer.