Liquid Crystal Display Common Electrode Stacking for Aperture Ratio
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Solution Overview
Problem
Liquid crystal display devices of the fringe field switching (FFS) mode face challenges in achieving a high aperture ratio and suppressing parasitic capacitance, which affects light transmittance and image quality due to the limited arrangement of common and pixel electrodes.
Innovation Solution
The liquid crystal display device features a common electrode disposed on the first insulating film covering the signal lines and scan lines, except for the pixel area, allowing for increased effective pixel area and reduced parasitic capacitance by covering at least one of the signal or scan lines, thereby enhancing the aperture ratio and preventing signal noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the common electrode is arranged on the same plane as scan lines to limit overlap, then the device complexity is reduced, but the aperture ratio decreases
Solution Approach 1:
The patent applies dimensionality change by stacking the common electrode on a different plane (lower layer) relative to the scan lines, rather than arranging them on the same plane. This vertical separation allows the common electrode to extend into the pixel area without increasing planar complexity, thereby increasing the aperture ratio while maintaining manageable device structure.
2Area of stationary object
If the pixel electrode is extended to overlap signal lines, then the aperture ratio increases, but parasitic capacitance increases causing vertical crosstalk
Solution Approach 1:
The patent resolves the parasitic capacitance issue by separating the pixel electrode and signal lines into different vertical planes. The pixel electrode is positioned in the upper layer while signal lines are in the lower layer, reducing their overlapping area in three-dimensional space. This dimensional separation allows the pixel electrode to extend further into the pixel area for higher aperture ratio while minimizing capacitive coupling and vertical crosstalk.
3Manufacturing precision
If the common electrode is limited by scan line arrangement, then the manufacturing precision is simplified, but the effective pixel area decreases
Solution Approach 1:
The patent enables the common electrode to extend into the pixel area by positioning it in a lower layer beneath the scan lines. This vertical arrangement removes the planar constraint that would otherwise limit the common electrode's extent, increasing the effective pixel area while maintaining straightforward manufacturing alignment procedures.
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 configuration enhances light transmittance, contrast, and image quality by stabilizing pixel potential and eliminating crosstalk, while preventing unstable operation from parasitic back-channels in the semiconductor layer.
Implementation Method 1
a common electrode and pixel electrode for applying an electric field to the liquid crystal layer
Implementation Method 2
liquid crystal display device of a fringe field switching (FFS) mode
Data Source
AI summary
There is provided a liquid crystal display device that includes a liquid crystal layer interposed between a first substrate and a second substrate and has on a first substrate side a common electrode and a pixel electrode for applying an electric field to the liquid crystal layer, the liquid crystal display device including: a plurality of scan lines and a plurality of signal lines; a drive element; a first insulating film; a common electrode; a second insulating film; and a pixel electrode, wherein the common electrode covers the pixel area except a formation area of the contact hole on the first insulating film and at least one of the scan line and the signal line.