LCD Array Substrate Electrode Overlap for Higher Transmittance
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Solution Overview
Problem
Liquid crystal display (LCD) devices suffer from low transmittance and aperture ratio due to large dark field regions at the edges of sub-pixel regions and light leakage between gate lines and pixel/common electrodes, resulting in reduced image quality.
Innovation Solution
The array substrate design includes a base substrate with gate lines, data lines, pixel electrodes, and common electrodes, where the common electrodes are positioned on the side of the pixel electrodes away from the base substrate, overlapping with gate lines to enhance the effective electric field and shield electric fields when the thin film transistor is off, thereby reducing light leakage and increasing transmittance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If common electrodes are positioned overlapping with gate lines, then transmittance increases and light leakage reduces, but device complexity increases due to overlapping structure design
Solution Approach 1:
The common electrode is positioned in a different spatial dimension (overlapping in planar projection but separated in vertical layering) from the gate line, allowing the electrode to extend into regions that would otherwise be occupied by gate lines without causing physical interference or short circuits. This dimensional arrangement increases transmittance by eliminating dark field regions while the layer separation maintains electrical insulation.
Solution Approach 2:
An insulating layer is introduced as an intermediary between the common electrode and the gate line where they overlap in projection. This insulating barrier prevents electrical shorting while allowing the common electrode to maintain its position for optimal transmittance and aperture ratio, thus resolving the conflict between electrical isolation requirements and optical performance requirements.
2Area of stationary object
If common electrodes overlap with gate lines to reduce dark field regions, then aperture ratio increases, but manufacturing precision requirements increase
Solution Approach 1:
By utilizing the vertical dimension for layer separation while allowing planar overlap, the design achieves high aperture ratio without requiring extremely precise lateral alignment. The insulating layer thickness in the vertical dimension becomes the critical dimension for preventing shorts, rather than requiring sub-micron lateral positioning accuracy between the common electrode and gate line.
Solution Approach 2:
The insulating layer serves as a mediator that decouples the alignment precision requirements. As long as the insulating layer maintains sufficient thickness and continuity, the common electrode can be positioned to maximize aperture ratio without concern for precise lateral alignment with gate lines, since the insulating barrier prevents electrical interference regardless of minor positioning variations.
3Object-generated harmful factors
If common electrodes are positioned to shield electric fields when transistor is off, then light leakage reduces, but device complexity increases
Solution Approach 1:
The common electrode serves multiple functions simultaneously: it acts as a transparent electrode for liquid crystal modulation, provides shielding to reduce light leakage in off-states by extending into gate line regions, and maintains electrical isolation through the insulating layer. This multi-functionality reduces light leakage without requiring additional dedicated shielding structures, thus avoiding increased device complexity.
Solution Approach 2:
The shielding function is merged with the common electrode structure itself rather than being implemented as a separate component. By extending the common electrode into the regions where gate lines are located and using the insulating layer for isolation, the design combines the electrical shielding function with the existing common electrode, eliminating the need for additional shielding elements and maintaining structural simplicity.
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 design effectively reduces the size of light leakage regions, increases transmittance by 10% or more, and enhances the aperture ratio by approximately 4%, improving the overall image quality of the LCD device.
Implementation Method 1
the common electrodes are positioned on the side of the pixel electrodes away from the base substrate, overlapping with gate lines to enhance the effective electric field and shield electric fields when the thin film transistor is off, thereby reducing light leakage
Implementation Method 2
overlapping with gate lines to enhance the effective electric field and shield electric fields when the thin film transistor is off
Data Source
AI summary
An array substrate has a plurality of sub-pixel regions. The array substrate includes a base substrate, gate lines disposed on a side of the base substrate and extending in a first direction, pixel electrodes each disposed in a respective one of the sub-pixel regions, and common electrodes disposed on a side, facing away from the base substrate, of the pixel electrodes and the gate lines. An orthographic projection of at least one common electrode on the base substrate at least partially overlaps with an orthographic projection of at least one gate line adjacent to the at least one common electrode on the base substrate, or a border of an orthographic projection of at least one common electrode on the base substrate partially overlaps with a border of an orthographic projection of at least one gate line adjacent to the at least one common electrode on the base substrate.