LCD Wiring Layout to Cut Parasitic Capacitance and Preserve Aperture
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Solution Overview
Problem
Current liquid crystal display panels face challenges in suppressing parasitic capacitance between wiring and pixels while maintaining a high aperture ratio, which is essential for achieving higher definition and efficient light transmission in display devices.
Innovation Solution
The liquid crystal display panel design incorporates a first substrate with pixel electrodes, thin-film transistors, and metal wiring lines arranged in specific layers and orientations, including extending portions and a common electrode, to minimize parasitic capacitance and maintain aperture ratio. The metal wiring lines are insulated from each other, and the common electrode is positioned closer to the surface in areas overlapping the third metal wiring, reducing electric field density and capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the definition of the display area is increased, then the display resolution is improved, but the area of the pixels is reduced leading to an increase in parasitic capacitance between wiring and pixels
Solution Approach 1:
The patent introduces a light-shielding metal layer positioned between the data wiring and the pixel electrode, utilizing the third dimension (vertical stacking) to shield the parasitic capacitance without occupying additional horizontal space. This dimensional approach allows the light-shielding metal to intercept electric field lines between the data wiring and pixel electrode, reducing parasitic capacitance while maintaining high display resolution.
Solution Approach 2:
The light-shielding metal acts as an intermediary element between the data wiring and the pixel electrode. It serves as a shielding layer that blocks the harmful electric field interaction between these two components, thereby reducing parasitic capacitance. The light-shielding metal is strategically positioned to mediate the electromagnetic interaction without interfering with the optical performance or pixel functionality.
2Measurement precision
If the definition of the display device is increased, then the number of pixels increases, but the occupation ratio of the wiring increases reducing the aperture ratio
Solution Approach 1:
The light-shielding metal is positioned in the vertical dimension between the data wiring and pixel electrode, rather than occupying horizontal space within the pixel area. This three-dimensional placement allows the shielding function to be achieved without reducing the aperture ratio, as the light-shielding metal does not block the optical path from the backlight through the liquid crystal layer to the viewer.
Solution Approach 2:
The light-shielding metal is strategically positioned only in specific regions where parasitic capacitance occurs between data wiring and pixel electrodes, rather than uniformly across the entire display. This localized shielding approach minimizes the impact on aperture ratio while effectively reducing parasitic capacitance in the critical areas where wiring intersects with pixels.
3Area of stationary object
If the line width of the black matrix layer is reduced to improve aperture ratio, then the aperture ratio is improved, but the parasitic capacitance between data wiring and pixel electrode is not suppressed
Solution Approach 1:
Instead of relying solely on the two-dimensional black matrix layer to address parasitic capacitance, the patent introduces a light-shielding metal layer in the third dimension (vertical stacking between data wiring and pixel electrode). This allows parasitic capacitance suppression without needing to increase the black matrix line width, thereby maintaining a high aperture ratio.
Solution Approach 2:
The patent separates the functions of light shielding and parasitic capacitance suppression. The black matrix layer handles light shielding, while the light-shielding metal layer specifically addresses parasitic capacitance reduction. This functional segmentation allows the black matrix line width to be minimized for high aperture ratio, while the light-shielding metal provides targeted parasitic capacitance suppression in the critical wiring-pixel interface region.
Data Source
AI summary
A liquid crystal display is provided and includes first and second substrates and liquid crystal layer therebetween; pixel electrode on first substrate; pedestal metal coupled to pixel electrode; semiconductor layer substantially U-shaped and coupled to pedestal metal at first coupling portion; scan line that extends in first direction and in layer different from semiconductor layer; signal line that extends in second direction different from first direction so as to three-dimensionally cross scan line, signal line being coupled to semiconductor layer at second coupling portion; and extending portion that is part of scan line and that protrudes from scan line, the extending portion extending along signal line, wherein: in first direction along a shorter side of each pixel unit, extending portion is adjacent to pedestal metal; and in second direction along a longer side of each pixel unit, length of extending portion is smaller than length of pedestal metal.