Asymmetric Parasitic Capacitance in IPS LCD Common Electrodes
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing in-plane switching (IPS) mode LCD devices suffer from a greenish phenomenon due to amplified common voltage fluctuations caused by parasitic capacitance between data and common electrodes, leading to inaccurate color rendering.
Innovation Solution
The LCD device design includes gate and data lines on a substrate with thin film transistors, pixel electrodes connected to the transistors, and common electrodes at both sides of sub-pixels, where the parasitic capacitance between the left and right data lines and common electrodes are made different to prevent voltage amplification, ensuring balanced voltage differences across sub-pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If common electrodes are placed adjacent to data lines in IPS mode LCD, then horizontal electric field is generated for liquid crystal switching, but parasitic capacitance causes common voltage fluctuations and greenish phenomenon
Solution Approach 1:
The patent applies asymmetry by making the distances from the data line to the left and right common electrodes unequal. Specifically, one distance is set to 1.5-3.0 times the other, creating asymmetric parasitic capacitance values that prevent voltage amplification and eliminate the greenish phenomenon while maintaining proper liquid crystal switching
Solution Approach 2:
The patent applies local quality by creating different parasitic capacitance characteristics at different locations. The left and right common electrodes are deliberately designed with different capacitance values relative to the data line, allowing each side to have optimized local electrical characteristics that prevent overall voltage fluctuations
2Force
If parasitic capacitance between data line and common electrode is increased, then coupling effect is enhanced, but common voltage is amplified causing color rendering errors
Solution Approach 1:
The patent resolves this contradiction by creating asymmetric parasitic capacitance where Cdc1 ≠ Cdc2. This asymmetry prevents the constructive interference that would amplify common voltage, while still maintaining sufficient coupling effects for proper signal transmission and liquid crystal control
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 prevents the greenish phenomenon by maintaining balanced voltage differences across sub-pixels, ensuring accurate color rendering and preventing common voltage shifts, thus enhancing the display's color accuracy.
Implementation Method 1
a liquid crystal layer, wherein a liquid crystal director is controlled by a fringe electric field formed between the relative electrode and the pixel electrode
Implementation Method 2
a liquid crystal director is controlled by a fringe electric field formed between the relative electrode and the pixel electrode
Implementation Method 3
parasitic capacitance Cdc may occur between the data line 15 and the common electrode 24 located in the outmost corner of the sub-pixel
Data Source
AI summary
A liquid crystal display device includes gate and data lines on a first substrate, wherein the gate lines cross the data lines to define sub-pixels, a thin film transistor to where the gate lines cross the data lines, a pixel electrode connected to the thin film transistor, a common electrode in a first sub pixel, wherein a first parasitic capacitance between a first data line arranged at the left side of the first sub-pixel and the common electrode is smaller than a second parasitic capacitance between a second data line arranged at the right side of the first sub-pixel and the common electrode; and a second substrate bonded to the first substrate with a layer of liquid crystal molecules therebetween, wherein the pixel electrode overlaps the common electrode and has a plurality of slits.