Touch Display Panel Coupling Capacitance Sensing
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Solution Overview
Problem
The thin film encapsulation layer in OLED displays becoming thinner positions the touch layer closer to the cathode, leading to coupling parasitic capacitance that adversely affects touch accuracy and driving in on-cell touch technology.
Innovation Solution
A touch display panel design featuring a metal grid structured touch sensing electrode layer that forms a coupling capacitor with the cathode, with touch signal lines led out from different regions to minimize space and enhance sensitivity, allowing the touch chip to detect touch operations by variations in the coupling capacitor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the encapsulation layer is made thinner to reduce module thickness, then the overall display thickness is reduced, but the touch layer positions closer to the cathode forming coupling parasitic capacitance that adversely affects touch driving accuracy
Solution Approach 1:
The patent converts the harmful coupling parasitic capacitance formed between the touch layer and cathode into a useful sensing mechanism. By detecting variations in this coupling capacitor caused by touch operations, the system transforms the previously adverse effect into the basis for accurate touch detection, thereby maintaining thin encapsulation layer design while ensuring touch driving accuracy
Solution Approach 2:
The patent changes the detection parameter from traditional mutual capacitance to coupling capacitance variation. By monitoring the change in coupling capacitor values when touch occurs, the system achieves accurate touch detection despite the thin encapsulation layer that causes strong coupling effects
2Device complexity
If the touch layer is positioned closer to the cathode to reduce module thickness, then the overall structure is more compact, but coupling parasitic capacitance forms between the cathode and touch electrodes which is unfavorable for touch driving
Solution Approach 1:
The patent transforms the harmful coupling parasitic capacitance into a beneficial sensing mechanism. Instead of trying to eliminate the coupling effect caused by close positioning, the system utilizes the coupling capacitor variation as the detection signal for touch operations, thereby maintaining structural compactness while ensuring touch driving reliability
Solution Approach 2:
The patent replaces traditional mutual capacitance detection with a coupling capacitance detection mechanism. This substitution allows the system to reliably detect touch operations even when the touch layer is positioned close to the cathode, as the coupling capacitance variation provides a clear detection signal
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 effectively prevents mutual capacitance signal absorption, improves touch sensitivity and stability, and increases the effective region for touch sensing, addressing the accuracy issues caused by parasitic capacitance.
Implementation Method 1
a coupling capacitor is formed between the touch sensing electrodes and the cathode, the touch chip determines whether there is a touch operation or not by detecting a variation of the coupling capacitor
Data Source
AI summary
A touch display panel is provided, which includes a thin film transistor substrate, a light-emitting layer, an encapsulation layer, and a touch layer. The light-emitting layer includes a cathode. The touch layer includes a plurality of touch sensing electrodes disposed in a same layer. The touch sensing electrodes are connected to a plurality of touch signal lines in a one-to-one correspondence, the touch signal lines are connected to a touch chip, a coupling capacitor is formed between the touch sensing electrodes and the cathode, and the touch chip determines whether there is a touch operation or not by detecting a variation of the coupling capacitor.