Backup TFT Pixel Repair via Laser Electrode Connection
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Solution Overview
Problem
Conventional methods for repairing defective pixels in TFT LCDs result in permanent defects, either converting bright points to dark or gray points, which do not significantly improve display performance.
Innovation Solution
A pixel structure utilizing a backup thin film transistor (TFT) with a top gate electrode is introduced, allowing for the replacement of a defective TFT with a second TFT, maintaining space efficiency and aperture ratio, and employing laser cutting and welding to reconnect electrodes for repair.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of repair
If conventional repair methods are used to repair defective pixels, then the defective pixel can be converted to a dark point or gray point, but the display performance is not significantly improved because the defective pixel remains permanent
Solution Approach 1:
A backup TFT is pre-configured in the pixel structure alongside the main TFT. The backup TFT remains inactive during normal operation but is ready to take over if the main TFT fails. This preliminary preparation enables functional repair rather than merely converting the defective pixel to a dark or gray point, thereby significantly improving display performance while maintaining repairability.
2Ease of repair
If a backup TFT is added to the pixel structure, then the pixel can be repaired by replacing the defective TFT, but the device complexity increases
Solution Approach 1:
The backup TFT shares common electrodes (source electrode, drain electrode, and gate electrode) with the main TFT. By merging these electrode structures, the patent reduces the number of separate components needed. The backup TFT is electrically isolated during normal operation through insulation films, but can be activated by breaking the insulation to connect its gate electrode to the scan line, enabling repair without significantly increasing overall device complexity.
Solution Approach 2:
The shared source, drain, and gate electrodes serve dual purposes: they function as electrodes for both the main TFT during normal operation and as electrodes for the backup TFT during repair mode. This multi-functionality allows the backup TFT to replace the main TFT when defective, reducing the need for additional dedicated components and minimizing the increase in device complexity.
3Ease of repair
If the backup TFT uses conventional electrode configuration, then it can replace the main TFT for repair, but the space efficiency decreases and aperture ratio is affected
Solution Approach 1:
The backup TFT shares common source, drain, and gate electrodes with the main TFT. This merging of electrode structures eliminates the need for separate dedicated electrodes for the backup TFT, significantly reducing the space required. The shared electrodes are positioned to allow both TFTs to coexist in the same pixel area, maintaining high space efficiency and aperture ratio while enabling functional repair capability.
Data Source
AI summary
A pixel structure includes a backup thin film transistor with a float gate electrode or a float drain electrode and a working thin film transistor. When the pixel of the working thin film transistor does not work, the backup thin film transistor replaces the working thin film transistor to drive the pixel. The method of repairing the pixel is to cut off the connection between the drain electrode of the working thin film transistor and the pixel electrode, and then to connect the main gate electrode or the drain electrode of the backup thin film transistor to the gate electrode or the drain electrode of the working thin film transistor, such that the backup thin film transistor can replace the working thin film transistor to drive the pixel electrode.