EL Display Defect Detection via Switching Transistor Voltage Control
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Solution Overview
Problem
In the manufacturing of electroluminescent (EL) display devices, it is difficult to determine whether defects are due to the organic EL light-emitting layer or the thin-film transistor (TFT), making precise defect repair challenging.
Innovation Solution
A method is introduced where a second voltage is applied to the EL element through the switching transistor, using an ON voltage on the gate signal line, and light emission is detected using an optical detector, allowing for differentiation between defects in the organic EL light-emitting layer and TFT defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a defect inspection process is performed to detect defective pixels, then defective pixels can be identified, but it cannot be determined whether the defect is due to the organic EL light-emitting layer or the TFT
Solution Approach 1:
The inspection method is segmented into multiple distinct inspection modes: a first inspection mode that applies a first voltage to the second terminal to detect defects in the organic EL light-emitting layer, and a second inspection mode that applies a second voltage to detect defects in the TFT. This segmentation allows each inspection mode to target specific components, thereby identifying both the presence and location of defects.
Solution Approach 2:
The switching transistor serves as an intermediary component that enables selective voltage application to the second terminal of the EL element. By controlling the switching transistor through the gate signal line, the inspection device can indirectly apply different voltages to test different components (EL layer vs. TFT), thus determining defect locations without directly accessing internal components.
2Reliability
If conventional lighting inspection is performed to check whether the panel is normally lighted, then light emission can be detected, but the location and possibility of defect repair cannot be determined
Solution Approach 1:
The inspection system dynamically switches between different inspection modes by controlling the switching transistor. In the first inspection mode, a first voltage is applied to inspect the organic EL light-emitting layer; in the second inspection mode, a second voltage is applied to inspect the TFT. This dynamic switching capability enables comprehensive defect localization, which directly informs repair decisions and improves ease of repair.
Solution Approach 2:
The inspection method changes the voltage parameter applied to the second terminal of the EL element depending on the inspection mode. By applying a first voltage in the first inspection mode and a second voltage in the second inspection mode, the system can differentiate between defects in the organic EL light-emitting layer and defects in the TFT, thereby determining both defect location and repairability.
3Productivity
If defect repair is performed without determining the defect location, then repair attempts can be made, but repair accuracy and yield improvement are limited
Solution Approach 1:
The inspection device performs preliminary inspection actions by applying different voltages in different inspection modes before the repair process. This preliminary action identifies both the presence and location of defects (whether in the organic EL light-emitting layer or the TFT), enabling precise repair planning and improving both repair precision and manufacturing yield.
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 approach enables precise identification of defect locations and possibilities, improving yield and reducing manufacturing costs by facilitating accurate defect repair in EL display panels.
Implementation Method 1
an organic EL light-emitting layer is disposed on the plurality of transistors. The EL display panel emits light as a result of supplying a current from the transistor to the organic EL light-emitting layer.
Data Source
AI summary
A plurality of pixels arranged in a matrix each include an EL element, a transistor, and a transistor. The EL element includes a cathode to which a first voltage is applied. The transistor includes a gate connected to a gate signal line, a source connected to an anode of the EL element, and a drain to which a second voltage having a potential higher than a potential of the first voltage is applied. A method for manufacturing the EL display device includes: applying the second voltage to the anode of the EL element via the transistor, by applying an ON voltage to the gate signal line; and detecting light emission by the EL element, using an optical detector, in a state in which the ON voltage is being applied to the gate signal line.