IPS LCD Array Substrate Asymmetric Electrode Layout
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Solution Overview
Problem
In-plane switching mode liquid crystal display (IPS) devices face issues with transmittance and aperture ratio due to the generation of a vertical electric field instead of a horizontal electric field in certain electrode portions, leading to inadequate liquid crystal molecule rotation and resulting in reduced display quality.
Innovation Solution
The design includes a substrate with a gate line, data lines forming pixel regions, thin film transistors, pixel electrodes, and common electrodes that overlap each other, along with shielding electrodes to generate both horizontal and vertical electric fields, reducing parasitic capacitance and direct current stress, and improving transmittance and aperture ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If common electrodes are formed with vertical portions extending perpendicularly from horizontal portions in IPS mode LCD, then the electrode structure can be formed, but a vertical electric field is generated instead of a horizontal electric field, causing inadequate liquid crystal rotation and reduced transmittance
Solution Approach 1:
The common electrode structure is changed from a symmetric perpendicular configuration to an asymmetric configuration where the common electrode extends in the same direction as the pixel electrode but does not overlap with it. This asymmetric layout ensures that only horizontal electric fields are generated, eliminating the problematic vertical electric field component while maintaining the IPS mode's horizontal switching mechanism.
Solution Approach 2:
The problem is solved by changing the spatial arrangement of the common electrode from a vertical extension (perpendicular dimension) to a horizontal extension (same dimension as pixel electrode). This dimensional change in electrode orientation ensures that the electric field is generated purely in the horizontal direction, consistent with IPS mode operation requirements.
2Illumination intensity
If shielding electrodes are added to reduce parasitic capacitance and improve display quality, then transmittance and aperture ratio are improved, but the device structure becomes more complex
Solution Approach 1:
The shielding electrode is designed to serve multiple functions simultaneously: it acts as a shield to reduce parasitic capacitance between the data line and pixel electrode, functions as an additional common electrode to generate horizontal electric fields, and serves as a structural support element. This multi-functionality reduces the need for separate components, thereby limiting the increase in device complexity while achieving improved transmittance and display quality.
3Area of stationary object
If the common electrode overlaps with the pixel electrode, then the electrode configuration can be compact, but direct current stress accumulates and causes signal delays and flicker
Solution Approach 1:
The overlapping configuration between common and pixel electrodes is completely eliminated by extracting the common electrode from the pixel electrode's vertical space. The common electrode is positioned in the same horizontal direction but in a non-overlapping spatial relationship, which removes the source of direct current stress and signal instability while maintaining a compact overall device footprint.
4Reliability
If vertical portions of common electrode are formed to connect to common line, then electrical connection is achieved, but vertical electric field generation occurs causing liquid crystal alignment issues
Solution Approach 1:
Instead of extending the common electrode vertically (perpendicular to the substrate) to achieve electrical connection, the design inverts the approach by extending the common electrode horizontally (parallel to the substrate) in the same direction as the pixel electrode. This inverted orientation ensures that the electric field is generated purely in the horizontal direction, maintaining proper liquid crystal alignment for IPS mode operation while still achieving reliable electrical connection to the common line.
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 the transmittance and aperture ratio of IPS mode LCD devices by ensuring proper liquid crystal molecule alignment and reducing signal delays and flicker, while minimizing direct current stress and light leakage.
Implementation Method 1
an in-plane switching (IPS) mode liquid crystal display device having an excellent property in viewing angle... a horizontal electric field is generated between the common electrode and the pixel electrode, and liquid crystal molecules are controlled by the horizontal electric field
Implementation Method 2
a liquid crystal display (LCD) device uses the optical anisotropy and polarization properties of liquid crystal molecules in a liquid crystal layer to display images
Implementation Method 3
the polarization of light through the liquid crystal molecules varies with the alignment direction of the liquid crystal molecules
Data Source
AI summary
An array substrate for an in-plane switching mode liquid crystal display device includes: a substrate; a gate line on the substrate; first and second common lines parallel to and spaced apart from the gate line; a data line crossing the gate line to define a pixel region; a thin film transistor connected to the gate line and the data line; a pixel electrode connected to the thin film transistor, the pixel electrode having a plate shape; a plurality of common electrodes connected between the first and second common lines, the plurality of common electrodes overlapping the pixel electrode; and first and second shielding electrodes parallel to the data line, the first and second shielding electrodes spaced apart from each other with respect to the data line.