Segmented In-Cell Touch Electrodes for Low-Parasitic Displays
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Solution Overview
Problem
Current display devices with touch functionality face challenges in implementing an in-cell touch structure efficiently, particularly in achieving accurate touch sensing while minimizing the impact of parasitic capacitance and maintaining display characteristics.
Innovation Solution
A display device design incorporating a substrate with sub-pixels, touch electrodes, charging transistors, sensing transistors, and a planarization layer, where the touch electrodes are formed of transparent conductive materials and integrated within the display structure, allowing for simultaneous formation with sub-pixel transistors and gate lines, thereby simplifying the process and reducing parasitic capacitance effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If touch electrodes are integrated within the display structure (in-cell touch), then the device complexity is reduced and manufacturing is simplified, but parasitic capacitance increases which degrades touch sensing accuracy
Solution Approach 1:
The touch electrode is divided into multiple segments (first touch electrode and second touch electrode) that are spatially separated and independently controlled. This segmentation allows the patent to reduce parasitic capacitance by distributing the capacitive load across multiple smaller electrodes rather than using a single large electrode, thereby improving touch sensing accuracy while maintaining the integrated in-cell structure
Solution Approach 2:
Different regions of the display structure are assigned different functions and properties. The touch electrodes are positioned at specific locations (first touch electrode above the light emitting element, second touch electrode below the substrate) with distinct electrical characteristics. This local differentiation allows optimization of touch sensing in specific areas while maintaining display performance in other regions, reducing overall parasitic capacitance impact
2Ease of manufacture
If touch electrodes are formed closer to the substrate, then the in-cell touch structure is achieved with simplified process, but the parasitic capacitance between touch electrode and other components increases
Solution Approach 1:
The touch electrode structure extends into the vertical dimension with electrodes positioned on both sides of the light emitting element (first touch electrode above, second touch electrode below). This three-dimensional arrangement allows the patent to achieve in-cell integration while managing parasitic capacitance through spatial distribution in multiple dimensions, as the capacitance is distributed across different vertical planes rather than concentrated in a single plane
3Device complexity
If charging transistors and sensing transistors are integrated on the same insulating layer, then device complexity is reduced, but interference between charging and sensing operations increases
Solution Approach 1:
The touch sensing operation uses periodic scanning of the segmented touch electrodes with alternating activation of charging and sensing transistors. By periodically switching between charging phase (activating charging transistors) and sensing phase (activating sensing transistors), the patent reduces interference between these two functions while maintaining their integration on the same insulating layer, thereby improving touch sensing reliability
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 approach enables accurate touch sensing by isolating the capacitance formed in touch electrodes from parasitic capacitance, improving sensing accuracy and maintaining display characteristics with a simplified and cost-effective in-cell touch structure implementation.
Implementation Method 1
during the touch sensing, only a quantity of electric charges formed on the touch electrode may be sensed regardless of the magnitude of the parasitic capacitance between the touch electrode and the other components
Data Source
AI summary
A display device includes a substrate including a plurality of sub pixels; a first touch electrode on the substrate and overlapping at least one subpixel from the plurality of sub pixels; a second touch electrode on the substrate and spaced apart from the first touch electrode and overlapping the at least one sub pixel; an insulating layer covering the first touch electrode and the second touch electrode; a plurality of charging transistors on the insulating layer and electrically connected to one of the first touch electrode and the second touch electrode; a plurality of sensing transistors on the insulating layer and electrically connected to one of the first touch electrode and the second touch electrode; a planarization layer covering the plurality of charging transistors and the plurality of sensing transistors; and a light emitting diode on the planarization layer.