Touch Display Device Reducing Parasitic Capacitance
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Solution Overview
Problem
The existing flexible OLED touch display devices suffer from high parasitic capacitance between touch electrodes and the cathode, leading to noise interference and reduced touch report rates due to the thin encapsulation layer between them.
Innovation Solution
Incorporating a common cathode and redundant cathodes in the same conductive layer, electrically insulated, with the touch layer positioned on the OLED display panel, where the orthographic projections of the touch electrodes partially overlap the redundant cathodes, and an encapsulation layer is placed between the common cathode and the touch layer to reduce parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the encapsulation layer thickness is reduced to achieve a thinner display device, then the device thickness is reduced, but the parasitic capacitance between touch electrodes and cathode increases
Solution Approach 1:
The cathode is segmented into a common cathode and multiple redundant cathodes that are electrically insulated from each other. This segmentation reduces the effective overlapping area between the touch electrodes and the cathode structures, thereby reducing parasitic capacitance while maintaining device thinness through the encapsulation layer
Solution Approach 2:
The encapsulation layer serves as an intermediary between the cathode structures and the touch electrodes. By optimizing its thickness and material properties, it provides electrical insulation that reduces parasitic capacitance coupling while maintaining mechanical integrity and device thinness
2Object-affected harmful factors
If the encapsulation layer thickness is increased to reduce parasitic capacitance, then the parasitic capacitance is reduced, but the device thickness increases
Solution Approach 1:
By segmenting the cathode into multiple insulated regions, the patent reduces parasitic capacitance without requiring a thick encapsulation layer. The segmentation itself creates electrical isolation that compensates for the thin encapsulation layer, maintaining both low parasitic capacitance and thin device profile
3Object-affected harmful factors
If redundant cathodes are added to reduce parasitic capacitance, then the parasitic capacitance is reduced, but the device complexity increases
Solution Approach 1:
The redundant cathodes serve multiple functions: they provide electrical insulation to reduce parasitic capacitance, maintain the OLED structure integrity, and ensure uniform charge distribution. This multi-functionality justifies the additional structural elements without proportionally increasing complexity
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 minimizes parasitic capacitance, reducing noise interference and maintaining a high touch report rate by ensuring the common cathode resistance is less than 30 ohms while maintaining a balanced parasitic capacitance.
Implementation Method 1
an encapsulation layer, and the encapsulation layer is located between the common cathode and the touch layer
Implementation Method 2
orthographic projections of the plurality of touch electrodes on the touch display device partially overlap orthographic projections of the plurality of redundant cathodes on the touch display device
Data Source
AI summary
The present disclosure provides a touch display device including an organic light emitting diode (OLED) display panel and a touch layer. The OLED display panel includes a common cathode and a plurality of redundant cathodes. The common cathode and the plurality of redundant cathodes are located in a same conductive layer. The touch layer is disposed on a side of the OLED display panel. The touch layer includes a plurality of touch electrodes. Orthographic projections of the touch electrodes on the touch display device partially overlap orthographic projections of the plurality of redundant cathodes on the touch display device.