Rear-Surface Touch Sensor Electrodes for Thin Display Devices
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Solution Overview
Problem
Current display devices with touch sensors face challenges in effectively sensing touch positions and pressures while maintaining a thin and aesthetically pleasing design, as existing solutions often require additional substrates and complex manufacturing processes.
Innovation Solution
A display device with a touch sensor system that includes a first sensing electrode on the rear surface of the display panel, a second sensing electrode on the front surface, and a flexible printed circuit board connecting both, utilizing conductive pastes and a light blocking layer to prevent external light reflection and minimize pattern recognition by the user.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional substrates and complex manufacturing processes are used to implement touch sensors, then sensing accuracy is improved, but device thickness and manufacturing complexity increase
Solution Approach 1:
The patent combines the touch sensor electrodes directly with the display panel substrate, merging two separate components (touch sensor and display panel) into a single integrated structure. This eliminates the need for additional substrates and complex assembly processes while maintaining sensing accuracy through direct integration of the sensing electrodes on the rear surface of the display panel.
2Measurement precision
If additional substrates and complex manufacturing processes are used to implement touch sensors, then sensing accuracy is improved, but device thickness increases
Solution Approach 1:
By integrating the touch sensor electrodes directly onto the display panel substrate, the patent eliminates the need for separate substrate layers, thereby reducing overall device thickness while maintaining sensing functionality.
Solution Approach 2:
The patent positions the sensing electrodes on the rear surface of the display panel, utilizing the z-dimension (depth/thickness direction) to place sensing components without increasing the front-facing footprint or requiring additional lateral space, thus maintaining a thin profile.
3Adaptability or versatility
If conductive patterns are added to the display panel, then touch sensing functionality is achieved, but light reflectance and pattern visibility increase
Solution Approach 1:
The patent converts the harmful effect of light reflection from conductive patterns into a benefit by strategically positioning the sensing electrodes on the rear surface of the display panel. This placement causes any reflected light to be directed away from the viewer's line of sight, transforming the potential visual defect into an acceptable or even beneficial outcome for touch sensing performance.
Solution Approach 2:
Instead of placing conductive sensing patterns on the front surface where they would be visible and cause light reflection issues, the patent inverts the approach by positioning the electrodes on the rear surface, thereby eliminating the visual and optical problems while maintaining sensing functionality.
4Measurement precision
If sensing electrodes are placed on the front surface, then touch position sensing is achieved, but pattern recognition by users occurs
Solution Approach 1:
The patent inverts the conventional approach by placing sensing electrodes on the rear surface of the display panel instead of the front surface. This inversion prevents users from visually recognizing the conductive patterns while maintaining accurate touch position sensing capability through the rear-surface electrode configuration.
Data Source
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Figure 3B
AI summary
There is provided a display device (DP). The display device includes a display panel (PP) for displaying an image on a front surface thereof and a pressure sensor (S2) disposed on a rear surface of the display panel to sense touch pressure of a user. The pressure sensor includes a first sensing electrode (PSa) and a second sensing electrode (PSb) insulated from each other to form a capacitance. The first sensing electrode is printed onto the rear surface of the display panel.