OLED Touch Display Panel Cathode Segmentation for Parasitic Capacitance Reduction
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Solution Overview
Problem
In existing OLED touch display panels, the close proximity of the cathode layer to the touch electrode layer results in large parasitic capacitance, leading to small variations in self-mutual capacitance, making it difficult to accurately identify touched positions.
Innovation Solution
The cathode layer is divided into separate sub-cathodes that also serve as touch electrodes, connected to a touch display chip through signal lines, and the OLED touch display panel is time-division driven using an array circuit layer to manage voltage differences during display and touch control periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the cathode layer and touch electrode layer are placed close together to reduce module thickness, then the module becomes lighter and thinner, but parasitic capacitance increases causing large noise interference and reducing touch detection accuracy
Solution Approach 1:
The patent introduces a buffer layer between the cathode layer and the touch electrode layer. This buffer layer acts as an intermediary that electrically isolates the two layers, reducing parasitic capacitance and noise interference while allowing the layers to remain in close proximity for maintaining thin module thickness.
Solution Approach 2:
The patent divides the cathode layer into multiple segmented cathodes corresponding to different sub-pixels. This segmentation reduces the overall parasitic capacitance by distributing the capacitive coupling across multiple smaller elements, thereby improving touch detection accuracy while maintaining the close-proximity structure.
2Length of moving object
If embedded touch technology is integrated into OLED display panels to achieve lighter and thinner modules, then the display becomes more compact, but the manufacturing process becomes more complicated with additional thin film layers and process flows
Solution Approach 1:
The patent merges the touch electrode layer with the cathode layer structure by using the cathode layer itself as the touch electrode. This integration eliminates the need for separate touch electrode layers and reduces the number of manufacturing steps while maintaining the embedded touch functionality.
Solution Approach 2:
The patent makes the cathode layer serve dual functions: as the electron injection electrode for OLED operation and as the touch electrode for touch sensing. This multi-functionality reduces the number of required layers and simplifies the manufacturing process while achieving both display and touch functionality.
3Measurement precision
If the cathode layer is divided into separate sub-cathodes that also serve as touch electrodes, then touch detection accuracy improves, but the structure becomes more complex
Solution Approach 1:
The patent divides the cathode layer into multiple segmented cathodes, with each segment corresponding to a sub-pixel and serving as an independent touch electrode. This segmentation improves touch detection accuracy by reducing parasitic capacitance and enabling precise touch location detection, while the segmentation pattern follows the existing sub-pixel layout to minimize additional structural 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 solution allows for accurate positioning of touched positions and reduces the module thickness by decoupling the cathode layer from the touch electrode layer, improving touch detection accuracy and module design.
Implementation Method 1
during a display period, an OLED circuit in the pixel circuit forward conducting to cause the OLED touch display panel to normally emit light
Implementation Method 2
Capacitive touch, by changing capacitance of panels, causes current variations which are converted into electric potential variations, so that users' touch coordinates may be determined
Data Source
AI summary
An OLED touch display panel and a driving method are provided. The OLED touch display panel includes a cathode layer. The cathode layer is divided into the two sub-cathodes separated from each other and also serving as touch electrodes. In a pixel circuit of the OLED touch display panel, under common operations of a first input terminal and a second input terminal fed with different voltages, the OLED touch display panel normally emits light or does not emit light.