In-cell Capacitive Touch Panel with Segmented Sensing Unit
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Solution Overview
Problem
Conventional in-cell capacitive touch panels face challenges in achieving high-resolution sensing due to high parasitic capacitance, which complicates the fabrication of large-size panels and limits accuracy.
Innovation Solution
The implementation of a sensing unit comprising a sensing liquid crystal capacitor and three transistors, connected to gate and readout lines, allows for high-resolution touch detection by generating a reference voltage and output current to determine touch positions, with a simplified readout unit and optimized capacitance design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional in-cell capacitive touch panels use traditional capacitive sensors, then the structure is simple, but the parasitic capacitance is high which limits measurement precision and makes large-size panel fabrication difficult
Solution Approach 1:
The sensing electrode is divided into multiple sub-electrodes arranged in an array, with each sub-electrode corresponding to a sensing unit. This segmentation allows independent capacitance measurement for each unit, improving touch detection accuracy while managing parasitic capacitance through distributed architecture
Solution Approach 2:
Different regions of the sensing electrode have different functions: some areas serve as sensing electrodes for touch detection, while others serve as common electrodes. The sensing electrodes are specifically optimized with segmented sub-electrodes to minimize parasitic capacitance in critical measurement zones
2Measurement precision
If the sensing unit uses a sensing liquid crystal capacitor with three transistors, then readout accuracy is improved, but the circuit structure becomes more complex
Solution Approach 1:
The three-transistor circuit performs multiple functions: one transistor charges the sensing capacitor, another transfers the signal, and the third controls the readout. This integrated approach achieves high readout accuracy while minimizing the number of additional components compared to traditional designs
Solution Approach 2:
The sensing liquid crystal capacitor acts as an intermediary element that couples the touch sensing function with the readout circuitry. The capacitor stores the capacitive signal from touch events and interfaces it with the transistor-based readout circuit, enabling accurate measurement without direct complex circuitry at each pixel
3Area of stationary object
If large-size touch panels are fabricated with traditional capacitive sensors, then the coverage area is increased, but the high parasitic capacitance makes fabrication difficult and reduces accuracy
Solution Approach 1:
The large-area sensing electrode is segmented into multiple small sub-electrodes distributed across the panel. Each sub-electrode has low individual parasitic capacitance, and the segmented architecture allows scalable fabrication for large panels while maintaining accuracy
Solution Approach 2:
The sensing units are arranged in a two-dimensional array pattern across the panel surface. This spatial distribution in multiple dimensions allows large coverage area while keeping each sensing unit compact and manageable for fabrication
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 enables high-resolution sensing with improved accuracy and a simpler readout circuit structure, suitable for large-size touch panels, while maintaining lightweight and high optical performance.
Implementation Method 1
The capacitance variation of the sensing liquid-crystal capacitors 14 is used to detect touch events and determine touch points
Implementation Method 2
A first transistor is connected to a first gate line and the sensing liquid crystal capacitor and is controlled by the first gate line to charge the sensing liquid crystal capacitor and generate a reference voltage
Implementation Method 3
The second transistor generates an output current to the third transistor according to the voltage of the first electrode of the sensing liquid crystal capacitor
Data Source
AI summary
An in-cell capacitive touch panel is disclosed. The present invention utilizes a sensing unit that comprises a sensing liquid crystal capacitor and three transistors to detect touch events. A first transistor is connected to a first gate line and the sensing liquid crystal capacitor and controlled by the first gate line to charge the sensing liquid crystal capacitor. A second transistor together with a third transistor functions as a capacitance-current converter. The second transistor generates an output current according to the voltage of a first electrode of the sensing liquid crystal capacitor. A second gate line controls the third transistor to transfer the output current through a readout line to a readout unit that determines the touch positions. Thus, the in-cell capacitive touch panel of the present invention can use a simple-structure readout circuit to achieve superior readout accuracy and is adaptive to various sizes of touch panels.