Common Voltage Polarity Inversion for LCD Afterimage Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Liquid crystal displays face issues with maintaining voltage levels at pixel electrodes, leading to deteriorated display characteristics and afterimages due to direct current bias voltages caused by parasitic capacitance.
Innovation Solution
Incorporating a common electrode on at least one of the substrates, with its voltage polarity inverted every two frames relative to a reference voltage, to prevent direct current bias and maintain desired gray scale display.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data voltage is applied to pixel electrode through thin film transistor, then image display is enabled, but voltage level cannot be maintained due to kickback voltage from parasitic capacitance
Solution Approach 1:
A common electrode is introduced as an intermediary element between the pixel electrode and the liquid crystal layer. This common electrode is connected to a common voltage generator that provides a reference voltage, mediating the electrical interaction and stabilizing the voltage environment for the pixel electrode, thereby reducing the impact of kickback voltage from parasitic capacitance.
Solution Approach 2:
The patent changes the voltage parameter by applying a specific common voltage to the common electrode that compensates for the kickback voltage effect. By adjusting the common voltage level and timing, the system maintains the pixel electrode voltage at the desired level despite the parasitic capacitance引起的电压波动.
2Object-generated harmful factors
If common voltage polarity is inverted every two frames, then direct current bias is prevented and afterimages are removed, but voltage control complexity increases
Solution Approach 1:
The common voltage polarity is inverted periodically every two frames rather than continuously or randomly. This periodic inversion prevents the accumulation of direct current bias in the liquid crystal layer and alignment layers, effectively removing afterimages while maintaining a relatively simple and predictable voltage control pattern that can be easily implemented through timing control.
3Productivity
If data voltage polarity is inverted every frame, then display refresh is achieved, but direct current bias forms in pixel electrode or alignment layer
Solution Approach 1:
The common electrode acts as a mediator that counteracts the direct current bias formed by continuous data voltage polarity inversion. By providing a stable reference voltage or controlled polarity inversion, the common electrode balances the electrical environment and prevents charge accumulation in the pixel electrode and alignment layers, allowing high refresh rates without afterimage formation.
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 solution improves display characteristics by preventing direct current bias and reducing afterimages, ensuring accurate gray scale representation and prolonged display performance.
Implementation Method 1
The common electrode is applied with a common voltage to form an electric field with the pixel electrode
Implementation Method 2
A data voltage is applied to the pixel electrode to form an electric field in the liquid crystal layer which controls the orientation of the liquid crystals, thereby displaying an image
Data Source
AI summary
A display apparatus includes a first substrate, a second substrate, a liquid crystal layer, and a common electrode. The first substrate includes a gate line, a data line insulated from the gate line while crossing the gate line, and a pixel electrode connected to the gate line and the data line. The second substrate faces the first substrate. The liquid crystal layer is interposed between the first substrate and the second substrate. The common electrode is disposed on at least one of the first substrate or the second substrate to form an electric field in cooperation with the pixel electrode. A data voltage applied to the pixel electrode has a polarity inverted every at least one frame with reference to a predetermined reference voltage, and a common voltage applied to the common electrode has a polarity inverted every at least two frames with reference to the reference voltage.