TFT Pixel Unit Asymmetric Electrode Overlap for Display Brightness
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Solution Overview
Problem
Conventional display devices have low light transmittance and brightness due to a large black matrix coverage area in pixel units, which reduces the display screen's brightness and can cause screen flicker issues from excessive drain electrode capacitance.
Innovation Solution
The pixel unit design features a TFT with an isosceles trapezoid active layer and electrodes, where the overlapped areas between the active layer and drain electrode, and between the active layer and source electrode, are optimized to reduce the black matrix coverage, increasing light transmittance and minimizing drain electrode capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the black matrix coverage area is increased to improve light shielding, then the light transmittance decreases, but the brightness of the display screen decreases
Solution Approach 1:
The patent applies asymmetry by designing the active layer and electrode overlapping areas with non-uniform dimensions. Specifically, the overlapping area between the active layer and drain electrode is made smaller than the overlapping area between the active layer and source electrode. This asymmetric design allows the black matrix to cover less area while maintaining proper TFT function, thereby increasing light transmittance and screen brightness without compromising light shielding effectiveness.
Solution Approach 2:
The patent applies local quality by optimizing the overlapping areas between the active layer and electrodes at different locations. The overlapping area with the drain electrode is reduced locally compared to the source electrode overlap, allowing the black matrix coverage to be minimized in specific regions while maintaining adequate shielding where needed. This localized optimization increases overall light transmittance.
2Reliability
If the overlapping area between active layer and drain electrode is increased to improve TFT performance, then the drain electrode capacitance increases, but screen flicker occurs
Solution Approach 1:
The patent applies asymmetry by creating an unequal relationship between the overlapping areas of the active layer with source and drain electrodes. The overlapping area with the drain electrode is specifically designed to be smaller than that with the source electrode. This asymmetric configuration reduces the drain electrode capacitance and minimizes screen flicker while preserving sufficient TFT performance through the larger source electrode overlap.
3Illumination intensity
If the black matrix coverage area is reduced to increase light transmittance, then the brightness increases, but the light shielding effectiveness decreases
Solution Approach 1:
The patent applies asymmetry in the electrode overlapping design to resolve this contradiction. By making the drain electrode overlap smaller than the source electrode overlap, the black matrix coverage area is reduced, increasing light transmittance and brightness. At the same time, the asymmetric configuration maintains adequate light shielding effectiveness by preserving sufficient overlapping areas in critical regions.
Data Source
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AI summary
A mask set, a pixel unit and a manufacturing method thereof, an array substrate and a display device are provided to overcome the problem of low brightness of a display screen of a display device. In the pixel unit, the maximum size value of an overlapped area between an active layer and a drain electrode of a thin-film transistor (TFT) in the direction parallel to data line is less than the size value of one side, overlapped with the data line, in an overlapped area between the active layer and a source electrode; and the source electrode is the portion of the data line disposed in an overlapped area between the active layer and the data line. The pixel unit has the advantages of a larger opening area and higher light transmittance. Thus, the brightness of a display screen of the display device comprising the pixel units can be enhanced. Moreover, the problem of screen flicker can be avoided to some extent, and hence the display quality of images can be improved.