In-cell Touch Panel Self-Capacitance Electrode Design
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Solution Overview
Problem
Capacitive in-cell touch panels face issues with reduced touch sensing accuracy due to human-body capacitance coupling with opposing capacitance, leading to a decreased signal-to-noise ratio, and increased manufacturing costs from additional processes on the TFT array substrate.
Innovation Solution
The implementation of self-capacitance electrodes in a single layer between the upper and lower substrates, insulated from each other, allows human-body capacitance to affect the entire self-capacitance, enhancing touch variation detection and reducing manufacturing costs by eliminating the need for additional layers on the TFT array substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mutual capacitance electrodes (two layers of ITO electrodes) are used, then touch function can be achieved, but human-body capacitance couples with opposing capacitance reducing signal-to-noise ratio and touch sensing accuracy
Solution Approach 1:
The patent extracts and eliminates the opposing capacitance component by using a single-layer self-capacitance electrode structure instead of the traditional two-layer mutual capacitance structure. This removes the source of harmful coupling between human-body capacitance and opposing capacitance, thereby improving signal-to-noise ratio and touch sensing accuracy.
Solution Approach 2:
The patent changes the capacitance detection parameter from mutual capacitance (Cm) to self-capacitance (Cs). By measuring the change in self-capacitance of the single-layer electrode when touched, the system avoids the signal degradation caused by opposing capacitance coupling while maintaining touch detection functionality.
2Reliability
If two layers of ITO electrodes are added on TFT array substrate, then mutual capacitance touch function is achieved, but manufacturing cost increases due to additional processes
Solution Approach 1:
The patent merges the touch electrode layer with the existing single-layer ITO structure in the TFT array substrate, rather than adding a separate two-layer touch electrode stack. This integration approach maintains touch functionality while eliminating the need for additional manufacturing processes and reducing overall production costs.
Solution Approach 2:
The single-layer ITO electrode serves dual functions: as the transparent conductive layer for the TFT array substrate and as the self-capacitance touch sensing electrode. This multi-functionality eliminates the need for separate touch electrode layers and reduces manufacturing complexity.
3Reliability
If two layers of ITO electrodes are used for mutual capacitance, then touch function is achieved, but overall module thickness increases
Solution Approach 1:
The patent combines the touch sensing function with the existing single-layer ITO electrode structure of the TFT array substrate. By integrating rather than adding, the design maintains thin-profile characteristics while achieving functional requirements.
Solution Approach 2:
Instead of adding touch electrodes on top of the display stack (which would increase thickness), the patent inverts the approach by utilizing the existing substrate electrode as the touch sensing element, thereby maintaining the original thin module profile.
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 improves touch sensing accuracy by increasing the signal-to-noise ratio and reduces manufacturing costs by simplifying the production process while maintaining high transmittance and productivity.
Implementation Method 1
a plurality of self-capacitance electrodes which are disposed between the upper substrate and the lower substrate and provided in a same layer and insulated from each other
Implementation Method 2
human-body capacitance coupling with opposing capacitance, leading to a decreased signal-to-noise ratio
Data Source
AI summary
An in-cell touch panel and a display device are provided. The touch panel includes: an upper substrate and a lower substrate provided opposite to each other, a plurality of self-capacitance electrodes which are disposed between the upper substrate and the lower substrate and provided in a same layer and insulated from each other, and a touch detection chip configured to determine a touch position by detecting capacitance variation of the self-capacitance electrodes in the touch time-period. Thus, an in-cell touch panel with higher touch accuracy, lower cost, higher productivity and higher transmittance can be obtained.