Touch Sensor Display Device with Common Electrode Shielding
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Solution Overview
Problem
Mutual capacitive touch sensors face challenges in accurately determining touch positions due to small mutual capacitance and large parasitic capacitance, leading to ripple voltage and DTX (Display to Touch Crosstalk) phenomena, which affect touch sensibility and accuracy.
Innovation Solution
The touch sensor integrated type display device features a lattice shape pattern for touch electrodes with windows surrounding pixel electrodes, with gate lines crossing over center portions of pixel electrodes, and a common electrode disposed between touch electrodes and data lines to continuously supply common voltage, reducing parasitic capacitance and eliminating DTX.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If mutual capacitive touch sensor is used to enable multi-touch perception, then touch functionality is enhanced, but parasitic capacitance from data lines and gate lines increases, reducing measurement precision
Solution Approach 1:
A common electrode layer is introduced as an intermediary between the touch electrodes and the data lines/gate lines. This common electrode acts as a shield that is connected to a stable reference potential, thereby isolating the touch sensing circuit from the parasitic capacitance generated by the data and gate lines, and improving touch position detection accuracy.
Solution Approach 2:
The parasitic capacitance problem is addressed by extracting the shielding function into a separate common electrode layer. This dedicated shielding layer is specifically designed to counteract the parasitic capacitance from data lines and gate lines, allowing the touch sensor to maintain high measurement precision while preserving multi-touch capability.
2Reliability
If time-division method is used to separate display and touch operations, then interference between display and touch is reduced, but response time increases and user experience deteriorates
Solution Approach 1:
The display and touch operations are performed simultaneously without time-division multiplexing. The common electrode layer enables this continuous operation by providing stable shielding during both display driving and touch sensing, eliminating the need to alternate between display and touch modes and thereby maintaining real-time touch responsiveness.
Solution Approach 2:
The common electrode serves as a mediator that enables simultaneous display and touch operations by shielding the touch electrodes from data line interference during active display periods, allowing continuous touch sensing without waiting for display refresh cycles.
3Length of moving object
If touch electrodes are positioned close to data lines for compact design, then device thickness is reduced, but parasitic capacitance increases causing ripple voltage and DTX phenomenon
Solution Approach 1:
The common electrode layer is positioned between the touch electrodes and the data lines to provide electrostatic shielding. This intermediary layer reduces the parasitic capacitance coupling between touch electrodes and data lines, preventing ripple voltage and DTX phenomenon while allowing the device to maintain a compact, thin profile.
Solution Approach 2:
The common electrode provides localized shielding specifically in the regions where touch electrodes are positioned near data lines. This targeted approach reduces parasitic capacitance at critical locations without requiring increased overall device thickness, maintaining compact design while eliminating harmful electromagnetic interference.
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 prevents ripple voltage and DTX, enhancing touch sensibility by minimizing parasitic capacitance between touch electrodes and data lines, allowing for accurate touch position detection without time-division methods.
Implementation Method 1
parasitic capacitance generated in the data lines and gate lines arranged in the display device are large
Implementation Method 2
changes in a capacitance of each independent pattern are measured, thereby deciding whether or not a touch operation is performed
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
Touch sensor integrated type display device improving a touch sensibility. The touch sensor integrated type display device includes a plurality of gate lines (GL1 to GL4) and data lines (DL1 to DL10) configured to cross over each other, a plurality of thin film transistors (TFT) disposed at crossings of the gate lines and the data lines, a plurality of pixel electrodes (P, P11 to P49) configured to be respectively connected to the thin film transistors and disposed between the data lines so that each of the gate lines crosses over pixel electrodes disposed on a same line, a plurality of touch electrodes (Tx11 to Tx15, Tx21 to Tx25, Tx31 to Tx35, Tx41 to Tx45, Tx51 to Tx55) configured to overlap the gate lines and the data lines without contacting and overlapping the pixel electrodes, a plurality of touch routing wires (TW11 to TW51, TW12 to TW52, TW13 to TW53, TW14 to TW54, TW15 to TW55) configured to be respectively connected to the touch electrodes and arranged in parallel with each other, and a common electrode (COM) configured to overlap the data lines, the gate lines, the pixel electrodes and the touch electrodes.