Test Element Group for OLED Cathode Resistance Inspection
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Solution Overview
Problem
Conventional methods for inspecting defects in large display devices, particularly those with top emission OLED structures, face challenges in accurately assessing the formation of auxiliary lines and cathode electrodes due to high resistance issues, which are exacerbated by the large area of the cathode electrode, leading to inefficiencies in defect detection and increased costs.
Innovation Solution
A display device with a test element group is designed, featuring a substrate with both a display area and a test area, where a test element group includes electrode patterns and layers that allow for the measurement of resistance through openings formed by laser drilling, enabling accurate defect inspection and reducing process costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the thickness of the cathode electrode is decreased to increase transmittance, then transmittance is improved, but resistance increases
Solution Approach 1:
The cathode electrode is divided into a main cathode electrode in the display area and multiple auxiliary cathode electrodes in the test area. This segmentation allows the main electrode to maintain thin thickness for high transmittance while auxiliary electrodes provide additional conductive paths to reduce overall resistance through parallel conduction.
Solution Approach 2:
A common electrode layer is introduced as an intermediary between the lower electrode and the auxiliary cathode electrodes. This common layer facilitates electrical connection and distributes current across multiple auxiliary electrodes, enabling resistance reduction without compromising the thinness of the main cathode electrode.
2Reliability
If auxiliary lines are formed to reduce resistance, then resistance is improved, but device complexity increases
Solution Approach 1:
The auxiliary cathode electrodes and common electrode layer are merged with the existing display structure in the test area. This integration allows resistance reduction functionality to be added without creating entirely separate components, thereby limiting the increase in device complexity while achieving the desired electrical performance.
Solution Approach 2:
The auxiliary cathode electrodes are arranged in multiple layers (first, second, and third auxiliary cathode electrodes at different vertical positions) rather than simply adding more lines in the same plane. This three-dimensional arrangement provides additional conduction paths without proportionally increasing planar complexity.
3Ease of manufacture
If conventional microscope inspection is used to check opening formation, then inspection is performed, but measurement precision is insufficient
Solution Approach 1:
The conventional optical microscope inspection method is replaced with an electrical resistance measurement system. Instead of visually examining opening formation through optical magnification, the invention uses electrical measurements through the test element group to detect defects, providing more precise and objective defect detection capability.
Solution Approach 2:
The test element group provides real-time electrical feedback about the quality of opening formation and electrode connections. By measuring resistance values through the auxiliary cathode electrodes and common electrode layer, the system continuously monitors manufacturing quality and provides quantitative data for defect detection, enabling more precise inspection compared to conventional visual methods.
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 allows for precise defect inspection of display devices by measuring resistance through the test element group, thereby reducing costs and improving the accuracy of defect detection in large display devices.
Implementation Method 1
a laser drilling process may be performed to connect the auxiliary line and the cathode electrode
Data Source
AI summary
A display device includes a substrate including a display area and a test area adjacent to the display area, a lower electrode disposed in the display area on the substrate, a common layer disposed on the lower electrode, an upper electrode disposed on the common layer; and a test element group. The test element group includes a plurality of electrode patterns disposed in a same layer as the lower electrode and in the test area on the substrate, a test common layer disposed in a same layer as the common layer and on the electrode patterns, where a plurality of openings is defined through the test common layer to expose a part of each of the electrode patterns, and an electrode layer disposed in a same layer as the upper electrode, on the test common layer, and in contact with the electrode patterns through the openings.