Scan Transistor Defect Detection in OLED Display Devices
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Solution Overview
Problem
Existing organic light emitting display devices face challenges in detecting defects in scan transistors due to foreign substances, leading to incorrect identification of defective subpixels and potential bright or dark points, which affects image quality and requires a method to accurately determine the coordinates of defective transistors post-shipping.
Innovation Solution
An organic light emitting display device with a defect detector that applies a data voltage when both the scan and sensing transistors are turned off to determine if charges are stored in the parasitic capacitor of the OLED, using a current comparator and analog-to-digital converter to identify defective scan transistors and store subpixel coordinates for processing as dark points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional defect detection methods are used, then defect detection is performed, but coordinates of defective subpixels cannot be correctly detected and defective circuit elements cannot be correctly determined
Solution Approach 1:
The patent applies preliminary action by performing defect detection during the manufacturing process rather than after shipping. The detection method involves applying a data voltage in a state where both scan and sensing transistors are turned off, then detecting charges in the parasitic capacitor before the device is shipped. This preliminary detection ensures accurate coordinate identification of defective subpixels while the device is still under controlled manufacturing conditions.
2Productivity
If scan transistor and sensing transistor are simultaneously driven, then normal operation is achieved, but defects in scan transistors cannot be detected
Solution Approach 1:
The patent applies segmentation by separating the detection function from the normal driving function. During normal operation, both scan and sensing transistors are driven simultaneously for display performance. For defect detection, a separate detection mode is implemented where both transistors are turned off and a specific detection voltage is applied to the data line, allowing independent testing of scan transistor functionality without interfering with normal display operations.
Solution Approach 2:
The patent uses the parasitic capacitor of the OLED as an intermediary to detect scan transistor defects. By applying a data voltage when both transistors are off and measuring the charges accumulated in the parasitic capacitor, the system can indirectly detect scan transistor defects without requiring the transistors to be in their normal driving state. This intermediary approach enables defect detection while maintaining normal driving operations.
3Reliability
If defect detection is performed after shipping, then post-manufacturing defects can be identified, but accurate coordinate information and circuit element identification become difficult
Solution Approach 1:
The patent performs defect detection as a preliminary action during the manufacturing process, specifically after the OLED module is assembled but before final shipping. This timing allows accurate identification of defective circuit elements and their coordinates while the device is still in a controlled manufacturing environment. The detection method involves applying a data voltage to the data line in a state where both scan and sensing transistors are turned off, then measuring charges in the parasitic capacitor to identify defective scan transistors with precise coordinate information.
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
Enables accurate detection of defective scan transistors and prevents image quality deterioration by correctly identifying and processing defective subpixels, ensuring proper image representation and maintaining display quality.
Implementation Method 1
detecting an amount of charges charged in a parasitic capacitor of the OLED to determine whether the scan transistor disposed in the subpixel is defective
Data Source
AI summary
The disclosure relates to an organic light emitting display device that can detect a defect in a scan transistor in the device in which the scan transistor and a sensing transistor simultaneously operate, and the device includes: an OLED in a subpixel; a driving transistor connected between the OLED and a driving voltage line; a scan transistor connected between a first node through which a data voltage is applied to the driving transistor and a data line; a sensing transistor connected between a second node between the driving transistor, the OLED, and a reference voltage line; and a defect detector for applying the data voltage in a state in which both the scan transistor and the sensing transistor are turned off and then detecting an amount of charges charged in a parasitic capacitor of the OLED to determine whether the scan transistor is defective due to foreign substances.