In-cell Touch Screen Panel with Segmented Cathode Layers
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Solution Overview
Problem
Current in-cell touch screen panels for OLED displays face challenges in manufacturing cost and thickness, and there is a need for an efficient touch control method that maintains accuracy and uniformity in organic light-emitting diode (OLED) displays.
Innovation Solution
An in-cell touch screen panel design with segmented cathode layers and a driving chip that outputs signals to sub-pixel circuits and cathode layers, allowing for touch scanning by detecting capacitance changes, ensuring accurate touch position determination and maintaining consistent operating states during both light-emitting and touch scanning phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If in-cell touch screen panel is used for OLED display, then manufacturing cost is reduced and thickness is decreased, but touch control accuracy and uniformity may be affected
Solution Approach 1:
The cathode layer is divided into multiple independent segments corresponding to different sub-pixel groups. Each segment can be independently controlled and scanned for touch detection, allowing the touch control function to be integrated into the display structure without requiring additional complete electrode layers, thus reducing manufacturing cost while maintaining touch accuracy
Solution Approach 2:
The segmented cathode layer serves dual functions: as the cathode electrode for OLED light emission and as the touch sensing electrode for capacitance-based touch detection. This multi-functionality eliminates the need for separate touch electrode layers, reducing both manufacturing cost and panel thickness while maintaining touch control accuracy through independent segment scanning
2Measurement precision
If segmented cathode layers are used for touch scanning, then touch position determination accuracy is improved, but signal interference between segments may occur
Solution Approach 1:
The driving chip scans different cathode layer segments in a periodic time-multiplexed manner, activating one segment at a time for touch detection. This periodic scanning approach allows accurate touch position determination for each segment while preventing signal interference between adjacent segments, as only one segment is active for sensing at any given moment
Solution Approach 2:
Before formal touch scanning, the system performs preliminary operations including displaying test patterns and conducting baseline capacitance measurements for each cathode segment. This preliminary characterization enables the system to establish reference values and compensate for manufacturing variations, ensuring accurate touch detection while minimizing interference effects
3Ease of manufacture
If cathode layers are used as touch electrodes, then manufacturing cost is reduced, but display brightness uniformity may be affected
Solution Approach 1:
The cathode layer is segmented into multiple independent regions corresponding to different sub-pixel groups. This segmentation allows independent control and compensation for each segment, enabling the system to correct brightness non-uniformity by adjusting driving signals for individual cathode segments while maintaining the cost advantage of using the cathode layer for both display and touch functions
4Measurement precision
If independent cathode layers for each sub-pixel group are implemented, then touch scanning accuracy is improved, but device complexity increases
Solution Approach 1:
The independent cathode layers for different sub-pixel groups serve dual purposes: as display electrodes for OLED operation and as touch sensing electrodes for capacitance-based touch detection. This multi-functionality allows the system to achieve accurate touch scanning through independent segment control while avoiding the need for additional dedicated touch electrode layers and associated complex signal routing
Solution Approach 2:
The display function and touch sensing function are merged into a single integrated structure where the cathode layers serve both purposes. By combining these functions into the existing display electrode structure rather than adding separate systems, the patent achieves improved touch scanning accuracy through independent segment control while minimizing the increase in overall device 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 reduces manufacturing costs, achieves thinner panel designs, and ensures accurate touch control with consistent brightness and capacitance readings, enhancing the performance and efficiency of OLED displays.
Implementation Method 1
each of the plurality of sub-pixels comprising an organic light-emitting device... the organic light-emitting device comprising an anode layer, a light-emitting layer and a cathode layer
Implementation Method 2
The driving chip outputs signals to signal terminals of each sub-pixel circuit and to the cathode layer of each sub-pixel group... allowing for touch scanning by detecting capacitance changes
Data Source
AI summary
An in-cell touch screen panel, a driving method thereof and a display device. A plurality of sub-pixels are grouped into sub-pixel groups, each of which includes at least two sub-pixels, and cathode layers of different sub-pixel groups are independent of one another. The cathode layers are reused as self-capacitance electrodes, and a driving chip determines a touch position by detecting a change in capacitance of the cathode layer, thereby achieving touch control functionality. The driving chip outputs, in a fourth phase, signals to respective cathode layers and signal terminals of each sub-pixel circuit, each of the signals is a superposition of the signal output in a third phase with a touch scanning signal.