Touch Sensor Shield Layer Parasitic Capacitance Reduction
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Solution Overview
Problem
Existing display devices with touch sensors face challenges in reducing thickness and minimizing parasitic capacitance, which affects signal sensitivity.
Innovation Solution
A display device design featuring a shield layer made of transparent conductive material between the second electrode and touch electrodes, with the same signal applied to the shield layer and touch electrodes, and an insulating layer to prevent parasitic capacitance, allowing for reduced thickness and enhanced signal sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a touch sensor is integrated into the display device, then touch functionality is added, but the device thickness increases
Solution Approach 1:
The touch sensor electrodes are integrated with the display electrodes, merging two functional layers into one. The first touch electrode is combined with the pixel electrode, and the second touch electrode is combined with the common electrode, eliminating the need for separate touch sensor layers and reducing overall device thickness.
Solution Approach 2:
The display electrodes serve dual functions: they act as both display electrodes for image rendering and touch electrodes for touch sensing. This multi-functionality allows the display device to provide both display and touch capabilities without adding extra layers, thereby maintaining thin profile.
2Length of stationary object
If touch electrodes are positioned close to display electrodes, then device thickness is reduced, but parasitic capacitance increases affecting signal sensitivity
Solution Approach 1:
An insulating layer is introduced as an intermediary between the touch electrodes and display electrodes. This insulating layer physically separates the two electrode types, reducing parasitic capacitance coupling while maintaining the thin overall structure. The insulating layer acts as a mediator that prevents direct electrical interaction between adjacent electrodes.
Solution Approach 2:
The same signal is applied to both the second touch electrode and the common electrode (display electrode), creating equipotential conditions. This reduces potential differences between adjacent electrodes, thereby minimizing parasitic capacitance effects and improving touch signal sensitivity.
3Reliability
If different signals are applied to touch electrodes and display electrodes, then electrode functions are optimized, but device complexity increases
Solution Approach 1:
The same signal is applied to both the second touch electrode and the common electrode, merging their signal inputs. This reduces the number of independent signal paths and simplifies the overall signal management system while maintaining proper electrode functionality through the shared signal.
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
The solution effectively reduces the thickness of the display device and minimizes parasitic capacitance, resulting in improved signal sensitivity and accuracy of touch input detection.
Implementation Method 1
a shield layer positioned between the second electrode and the touch electrodes and including a conductive material
Implementation Method 2
The shield layer may be positioned below the touch electrodes with an insulating layer therebetween
Data Source
AI summary
A display device including a touch sensor is disclosed. In one aspect, the display device includes a lower substrate and an upper substrate opposing each other and a first electrode, an electro-optical active layer, and a second electrode sequentially formed over the lower substrate. The display device also includes a plurality of touch electrodes formed below the upper substrate and over the second electrode and a shield layer interposed between the second electrode and the touch electrodes. The shield layer is formed at least partially of a conductive material.