Touch Display Electrode Layout for Lower Parasitic Capacitance
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Solution Overview
Problem
The reduction in distance between display panels and touch electrodes in touch display devices leads to increased parasitic capacitance, deteriorating touch performance, which is a limiting factor in maximizing the display panel's capabilities.
Innovation Solution
The implementation of a structure where first and second touch electrode units are disposed on different substrates, with the second substrate being bonded to the first via an adhesive layer, and the use of passivation layers to maintain touch performance, particularly in large-area touch panels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the distance between display panel and touch electrodes is reduced, then device thickness is decreased, but parasitic capacitance increases and touch performance deteriorates
Solution Approach 1:
The patent introduces an intermediate layer structure between the display panel and touch electrodes, adding a dimensional separation that reduces parasitic capacitance while maintaining compact overall device thickness. The touch electrodes are positioned on a separate substrate (CF substrate) that is optically coupled to the display panel, creating a spatial separation in the Z-direction that reduces capacitance coupling.
Solution Approach 2:
The patent employs an intermediate optical coupling layer and intermediate substrate structure between the display panel and touch electrodes. This intermediary structure acts as a capacitor separator, reducing parasitic capacitance while maintaining the electrical and optical functionality of the touch sensing system.
2Device complexity
If touch electrodes are placed closer to display panel, then manufacturing complexity is reduced, but parasitic capacitance increases
Solution Approach 1:
The patent segments the touch display structure into distinct functional layers: display panel, intermediate optical coupling layer, and touch sensor layer on separate substrate. This segmentation allows independent optimization of each layer, reducing parasitic capacitance between display and touch components while maintaining manufacturing feasibility through standardized layer fabrication processes.
3Object-generated harmful factors
If distance between display panel and touch electrodes is increased, then parasitic capacitance is reduced, but device thickness increases
Solution Approach 1:
The patent utilizes thin film structures for the optical coupling layer and intermediate substrates, achieving sufficient electrical separation to reduce parasitic capacitance while maintaining minimal physical thickness. The thin film approach allows effective capacitance reduction without proportionally increasing overall device volume.
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 effectively reduces parasitic capacitance, enhancing touch performance and maintaining it even in large-area touch panels by increasing the distance between the display panel and touch electrodes.
Implementation Method 1
a second substrate bonded by an adhesive layer to a first substrate
Implementation Method 2
an encapsulation layer disposed on the second electrode of the display panel
Implementation Method 3
parasitic capacitance increases when a distance between the display panel and the touch electrodes is reduced
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
Discussed is a display device including a first substrate; a display panel including first and second electrodes disposed on the first substrate, and a light-emitting layer located between the first electrode and the second electrode; an encapsulation layer disposed on the second electrode of the display panel; a first touch electrode unit disposed on the encapsulation layer and extending in one of a first direction and a second direction intersecting with the first direction; and a first passivation layer disposed on the first touch electrode unit.