Capacitive Touch Pressure Sensor Integrated in Backlight Unit
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Solution Overview
Problem
Current touch screen technologies can detect touch position but struggle to accurately measure touch pressure without degrading the performance of the display module.
Innovation Solution
A smartphone configuration that includes a touch sensor panel with a pressure sensor integrated into the backlight unit, utilizing a spacer layer and electrodes to detect changes in capacitance caused by pressure, allowing for precise measurement of touch pressure while maintaining display quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a pressure sensor is integrated into the display module, then touch pressure detection capability is improved, but the display module performance may be degraded
Solution Approach 1:
The patent combines the pressure sensor with the backlight unit structure, integrating multiple functions (light emission and pressure sensing) into a single modular component. The pressure sensor is positioned between the reflective sheet and the second cover layer of the backlight unit, allowing simultaneous pressure detection and display functionality without requiring separate sensor integration that would compromise display performance
Solution Approach 2:
The patent introduces a capacitor structure as an intermediary element between the pressure sensor electrodes and the display panel. The capacitor includes a first electrode connected to the pressure sensor and a second electrode positioned within the LCD panel, with a dielectric layer between them. This intermediary capacitor structure enables pressure signal transmission while electrically isolating the pressure sensor from the display panel, preventing interference with display performance
2Measurement precision
If the pressure sensor is placed close to the display panel for accurate detection, then measurement precision is improved, but the structural complexity increases
Solution Approach 1:
The patent makes the backlight unit multi-functional by integrating the pressure sensor into its structure. The backlight unit not only provides illumination but also serves as the housing and mounting structure for the pressure sensor. The second cover layer of the backlight unit acts as both a protective element for the display and a substrate for mounting the pressure sensor electrodes, eliminating the need for separate sensor mounting structures
Solution Approach 2:
The patent divides the pressure sensor into two separate electrode layers (first electrode connected to pressure sensing circuitry, second electrode forming part of the capacitor) positioned at different locations within the backlight unit structure. This segmentation allows each electrode to be optimally positioned for its specific function while maintaining a compact overall structure
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
Enables accurate detection of touch pressure without compromising the display module's performance, enhancing user interaction by providing both touch position and pressure sensitivity.
Implementation Method 1
a magnitude of a touch pressure is detected based on a change amount of capacitance that is output from the pressure sensor and that is changed according to a distance between the pressure sensor and an electrode located within the LCD panel
Implementation Method 2
a touch sensor which senses touch in a capacitive manner; wherein a driving signal is applied to the touch sensor and a touch position is detected by a sensing signal output from the touch sensor
Data Source
AI summary
A smartphone may include a first cover layer and an LCD panel. A backlight unit may be located under the LCD panel. A touch sensor may sense touch in a capacitive manner. The backlight unit may include a pressure sensor and a spacer layer. The pressure sensor includes a plurality of electrodes formed in a single layer attached on the second cover layer and spaced apart from the reflective sheet. A driving signal is applied to the touch sensor and a touch position is detected by a sensing signal. A magnitude of a touch pressure is detected based on a change amount of capacitance which is output from the pressure sensor and which is changed according to a distance between the pressure sensor and an electrode located within the LCD panel. The pressure sensor is attached on the second cover layer as an integral sheet including insulation layers.