In-cell Touch LCD Common Electrode Noise Shielding
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Solution Overview
Problem
In-cell capacitive touch panels suffer from a low signal-to-noise ratio due to the proximity of the touch layer to the common electrode layer in LCD screens, which is affected by electrical noise during image display.
Innovation Solution
The introduction of a common electrode layer with independent first and second common electrodes, where at least a portion of the driving lines overlap with the first common electrode and sensing lines overlap with the second common electrode, allowing for specific touch control signals to be applied during a designated touch control time to equalize electric potentials and shield noise interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the touch layer is integrated close to the common electrode layer in the LCD screen, then the structure is simplified and thickness is reduced, but the signal-to-noise ratio deteriorates due to electrical noise interference
Solution Approach 1:
The common electrode layer is segmented into first and second common electrodes that are electrically isolated from each other. The first common electrode overlaps with driving lines while the second common electrode overlaps with sensing lines, allowing independent voltage control to shield noise while maintaining structural integration
Solution Approach 2:
The first and second common electrodes act as intermediary shielding layers between the touch layer and the LCD screen noise sources. By controlling their voltages to match the driving and sensing lines respectively, they mediate and block electrical noise interference without requiring additional external shielding structures
2Measurement precision
If additional shielding layers are added to improve signal-to-noise ratio, then noise shielding is enhanced, but the device structure becomes more complex and thicker
Solution Approach 1:
The common electrode layer serves dual functions: it maintains the LCD display function while simultaneously providing noise shielding for the touch panel. By segmenting it into first and second common electrodes with different voltage controls, it performs both display and noise protection roles without requiring separate dedicated shielding layers
Solution Approach 2:
The noise shielding function is merged with the existing common electrode layer of the LCD screen rather than being implemented as a separate additional layer. This combines the display and touch shielding functions into a single integrated structure, avoiding increased device thickness and complexity
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 signal-to-noise ratio of the touch panel by effectively shielding noise generated by the LCD screen, without the need for additional shielding layers, simplifying the LCD apparatus structure.
Implementation Method 1
A first touch control signal is applied to the first common electrode and a second touch control signal is applied to the second common electrode during a touch control time, so that the first common electrode has an electric potential equal to that of the driving line and the second common electrode has an electric potential equal to that of the sensing line. Therefore, noise generated by the LCD screen may be shielded
Data Source
AI summary
An in-cell touch panel LCD module (100) and a method for driving the same includes a common electrode layer including first and second common electrodes. A control circuit divides the frame time period into a display time period and a touch control time period. A display signal is applied to the common electrode layer during the display time period for a normal LCD display. First and second touch control signals are applied to the first and second common electrodes, respectively, during the touch control time period, so that the electric potential of the first common electrode equals to that of the driving line and the electric potential of the second common electrode equals to that of the sensing line.