Shield Line Reduces Parasitic Capacitance in Touch Display
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Solution Overview
Problem
The proximity of conductive layers in display devices with touch sensors leads to parasitic capacitance, which increases touch-driving load and deteriorates touch-sensing accuracy, especially when the distance between these layers is short.
Innovation Solution
A display device with a touch sensor that employs a touch-driving circuit operating in mutual-capacitance mode for the touch-driving and touch-sensing lines, and self-capacitance mode for overlapping lines, with a load-free driving signal supplied to the shield line to minimize parasitic capacitance and enhance touch-sensing performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the conductive layer of the display device and the touch sensor are placed close to each other, then the touch sensor can be integrated more compactly, but parasitic capacitance increases and touch-sensing accuracy deteriorates
Solution Approach 1:
A shield line is introduced as an intermediary element between the touch sensor and the conductive layer of the display device. This shield line acts as a mediator that blocks or reduces the parasitic capacitance coupling between the touch sensor electrodes and the underlying conductive layers, thereby maintaining touch-sensing accuracy while allowing compact integration.
Solution Approach 2:
The parasitic capacitance problem is addressed by extracting or separating the shielding function from the main touch sensing structure. The shield line is implemented as a distinct conductive element that is specifically dedicated to reducing parasitic effects, rather than trying to solve the problem through the touch sensor electrodes themselves.
2Measurement precision
If parasitic capacitance is reduced by increasing distance between conductive layers, then touch-sensing accuracy improves, but device thickness and complexity increase
Solution Approach 1:
Rather than uniformly increasing the distance between all conductive layers throughout the device, the shield line provides localized capacitance reduction only in the critical regions where touch sensing occurs. This allows the majority of the device structure to maintain its original compact design while achieving improved touch-sensing accuracy where needed.
3Measurement precision
If a shield line is added to reduce parasitic capacitance, then touch-sensing performance improves, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The shield line is integrated into the existing touch sensor fabrication process and layer structure. Rather than being a separate additive component requiring additional manufacturing steps, the shield line is formed using the same thin-film deposition and patterning techniques as the touch sensor electrodes, allowing it to be manufactured concurrently with the main touch sensor structure.
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 reduces parasitic capacitance and noise, thereby improving touch-sensing accuracy and performance by minimizing voltage differences between shield and touch lines, allowing for more precise touch coordinate detection.
Implementation Method 1
a touch-driving circuit configured to drive a touch-driving line and a touch-sensing line, which are disposed on an encapsulation unit covering a light-emitting element, in a mutual-capacitance mode
Implementation Method 2
to drive at least one of the touch-driving line or the touch-sensing line overlapping a shield line in a self-capacitance mode
Implementation Method 3
parasitic capacitance is formed at a region at which the conductive layers of the display device and the touch sensor overlap each other. This parasitic capacitance increases a touch-driving load and deteriorates touch-sensing accuracy
Data Source
AI summary
The present disclosure provides a display device having a touch sensor for securing improved touch-sensing performance. The display device having a touch sensor includes a touch-driving circuit configured to drive a touch-driving line and a touch-sensing line, which are disposed on an encapsulation unit covering a light-emitting element, in a mutual-capacitance mode and to drive at least one of the touch-driving line or the touch-sensing line in a self-capacitance mode, and the touch-driving circuit supplies a load free driving signal to a shield line overlapping the touch-driving line and the touch-sensing line, thereby securing improved touch-sensing performance.