Integrated Touchscreen Electrodes With Guard Domains for Accurate Sensing
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Solution Overview
Problem
Capacitive touch sensor panels face errors due to parasitic or stray capacitances between touch node electrodes and other components, which can introduce offsets and reduce the accuracy of touch detection.
Innovation Solution
An integrated touchscreen design that includes light emitting diodes (LEDs) or organic light emitting diodes (OLEDs), display chiplets, and touch chiplets, with an integrated touch and display controller that provides control and timing signals, and reads out touch data, while using electrodes that can operate as both display and touch functionality nodes, and employs a guard power domain to reduce parasitic capacitances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If capacitive touch sensor panels use transparent conductive plates (such as ITO) to detect touch, then the panel achieves substantial transparency and can be overlaid on display to form touch screen, but parasitic or stray capacitances exist between touch node electrodes and other components which introduce errors and offsets into touch outputs
Solution Approach 1:
A guard ring structure is introduced as an intermediary element between the touch node electrodes and other components. The guard ring is driven at the same potential as the touch node electrode, creating an equipotential region that redirects stray electric field lines and prevents them from coupling to nearby conductive structures. This intermediary structure effectively isolates the touch sensing signal from parasitic capacitance effects while maintaining the transparency of the ITO conductive plates.
Solution Approach 2:
The patent converts the harmful parasitic capacitance effect into a beneficial shielding mechanism. By deliberately introducing guard rings driven at the same potential, the stray electric fields that would normally cause errors are redirected and contained within controlled regions. The parasitic capacitance paths are transformed into protective shielding zones that actively cancel out interference, turning the previously harmful effect into a useful error-compensation mechanism.
2Device complexity
If touch sensing circuitry is integrated into display pixel stackup, then device complexity is reduced and manufacturing is simplified, but parasitic capacitances between touch nodes and display components increase
Solution Approach 1:
The guard ring structure serves as a spatial and electrical intermediary that separates touch sensing functions from display functions within the integrated stackup. By positioning guard rings between touch node electrodes and display components (such as OLED pixels and connection structures), the design creates protective zones that prevent direct capacitive coupling. This allows tight integration without sacrificing touch sensing precision, as the guard rings act as buffer zones that electrically isolate sensitive touch nodes from noisy display structures.
Solution Approach 2:
The patent applies local quality enhancement by adding guard ring structures specifically at critical locations where parasitic capacitance problems occur, rather than uniformly modifying the entire display stackup. The guard rings are strategically positioned around touch node electrodes that are most susceptible to interference from nearby display components. This localized approach maintains overall device integration while providing targeted protection against parasitic effects in problem areas.
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 improves the accuracy and reliability of touch sensing by minimizing parasitic capacitance effects, enhancing the signal-to-noise ratio and dynamic range, and allowing for simultaneous sensing of touch nodes without aggregation or storage, thereby improving the detection of touch and proximity events.
Implementation Method 1
capacitive-type touch sensing systems, fringing electric fields used to detect touch can extend beyond the surface of the display
Implementation Method 2
in some capacitive-type touch sensing systems, fringing electric fields used to detect touch can extend beyond the surface of the display, and objects approaching near the surface may be detected near the surface without actually touching the surface
Data Source
AI summary
An integrated touchscreen can include light emitting diodes or organic light emitting diodes (LEDs/OLEDs), display chiplets and touch chiplets disposed in a visible area of the integrated touch screen. For example, the LEDs/OLEDs, display chiplets and touch chiplets can be placed on a substrate by a micro-transfer tool. The integrated touchscreen can also include electrodes disposed in the visible area of the integrated touch screen. The electrodes can be capable of providing display functionality via the one or more display chiplets during display operation (e.g., operating as cathode terminals of the LEDs during the display operation) and capable of providing touch functionality via the touch chiplets during touch operation (e.g., touch node electrodes can be formed from groups of the electrodes and sensed). In some examples, the touch node electrodes can be formed and coupled to touch chiplets via the display chiplets.