Shielding Layer AC Voltage for LCD Impurity Ion Control
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Solution Overview
Problem
LCD devices face issues with parasitic capacitance affecting voltage accuracy and gray scale display quality, and image sticking due to impurity ions in the liquid crystal layer, which current methods attempt to address with high costs and long adjustment periods.
Innovation Solution
An LCD device with a CF substrate, a TFT substrate, and a liquid crystal layer, where an AC voltage control signal is applied to the shielding layer to generate an alternating electric field that pushes impurity ions in the liquid crystal layer, reducing their adsorption on electrodes and improving display quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a DC common voltage is applied to the common electrode, then the liquid crystal molecules can be driven to change arrangement, but impurity ions in the liquid crystal layer are adsorbed on the pixel electrode and common electrode, causing image sticking
Solution Approach 1:
The patent applies a periodic AC voltage signal to the shielding layer, creating an alternating electric field that periodically shifts impurity ions away from the pixel electrode and common electrode surfaces. This periodic action prevents ion adsorption while maintaining the DC common voltage necessary for liquid crystal molecule driving, thus eliminating image sticking without sacrificing display quality
Solution Approach 2:
The shielding layer acts as an intermediary element between the AC voltage source and the liquid crystal layer. By applying AC voltage to this intermediate shielding layer rather than directly to the liquid crystal layer, the patent creates an alternating field that mitigates ion adsorption on the electrodes while preserving the primary DC driving function of the liquid crystal display
2Speed
If the TFT turns on or off sharply, then the data line can quickly charge or discharge the pixel electrode, but parasitic capacitance Cgd generates feed-through voltage that affects voltage accuracy and gray scale display
Solution Approach 1:
The shielding layer serves as an intermediary that couples the AC voltage signal to the liquid crystal layer without directly interfering with the DC voltage charging process. This intermediary AC field compensates for the harmful effects of parasitic capacitance Cgd by counteracting the feed-through voltage, thereby maintaining voltage accuracy while preserving fast charging speed
Solution Approach 2:
The patent introduces AC voltage as an additional parameter to the existing DC operating conditions. By superimposing an AC signal on the DC common voltage through the shielding layer, the system compensates for voltage deviations caused by parasitic capacitance, achieving both fast response and accurate voltage 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
The solution effectively alleviates image sticking and enhances display quality with reduced costs and shorter adjustment times by preventing impurity ion adsorption on electrodes, maintaining the horizontal electric field's integrity.
Implementation Method 1
An AC voltage control signal is applied to the shielding layer to generate an alternating electric field that pushes impurity ions in the liquid crystal layer
Data Source
AI summary
An LCD device includes a color filter (CF) substrate, a thin film transistor (TFT) substrate and a liquid crystal layer. The CF substrate includes a first transparent substrate, a CF layer, a black matrix and a shielding layer. The TFT substrate includes a second transparent substrate, a pixel electrode, a common electrode, and an insulating layer disposed between the pixel electrode and the common electrode. A control signal in the form of an AC voltage is provided to the shielding layer of the CF substrate, and a DC common voltage is provided to the common electrode. An alternating electric field is generated between the AC voltage of the control signal of the shielding layer and the DC common voltage of the common electrode to push impurity ions existed in the liquid crystal layer to swing up and down in the liquid crystal layer.