Force Sensor Electrode Layout for Accurate Light-Press Detection
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Solution Overview
Problem
Current force sensors in display devices have a wide resistance value sensing range and high degree of scattering, leading to increased manufacturing costs and potential errors in force sensing, particularly when detecting lighter forces.
Innovation Solution
The force sensor design includes a first and second force sensing layer, with the second force sensing layer contacting the second driving and sensing electrodes, reducing the resistance value range and scattering by varying the contact area based on applied force, and utilizing auxiliary electrodes to enhance uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional force sensing layer is used with large contact area, then the sensing range is wide, but the resistance value scattering is high and manufacturing cost increases
Solution Approach 1:
The force sensing layer is divided into multiple separate sensing regions rather than a single large contact area. Each sensing region corresponds to specific electrodes, creating discrete sensing zones that reduce overall resistance scattering while maintaining adequate sensing range through the collective effect of multiple regions.
Solution Approach 2:
Different regions of the force sensing layer have different contact characteristics with driving and sensing electrodes. By optimizing the local contact area and distribution in different regions, the patent achieves uniform resistance values across the sensing layer while maintaining appropriate sensing range, thereby improving measurement precision without excessive complexity.
2Reliability
If the contact area between force sensing layer and electrodes is increased, then the sensing range is improved, but the degree of scattering increases
Solution Approach 1:
The contact area between the force sensing layer and electrodes is designed to dynamically adjust based on applied force. When force is applied, the sensing layer deforms to increase contact area with the electrodes, providing reliable sensing. When no force is applied, the contact area is reduced, minimizing resistance scattering and improving manufacturing precision.
Solution Approach 2:
The patent changes the contact area parameter of the force sensing layer based on the magnitude of applied force. By making the contact area variable rather than fixed, the system achieves both high reliability for force detection and low scattering for manufacturing precision across different force conditions.
3Measurement precision
If the resistance value sensing range is reduced, then the accuracy for lighter forces is improved, but the sensing capability for heavier forces is limited
Solution Approach 1:
The patent introduces a temporal dimension to the sensing process by sequentially activating different sensing regions. For light forces, specific regions with optimized contact areas provide high precision measurement. For heavier forces, additional regions are activated or the system transitions to a different measurement mode, thereby achieving both precision for light forces and versatility for heavy forces without compromising either.
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 design reduces the resistance value range and scattering, enhancing the accuracy of force sensing while lowering manufacturing costs and preventing errors in detecting lighter forces.
Implementation Method 1
The resistance value sensed by the force sensor changes depending on the force pressed by a user
Data Source
AI summary
A force sensor, includes: a first substrate and a second substrate; a first driving electrode, a second driving electrode, a first sensing electrode, and a second sensing electrode on one surface of the first substrate facing the second substrate; a first force sensing layer on one surface of the second substrate facing the first substrate; and a second force sensing layer contacting the second driving electrode and the second sensing electrode, wherein the first force sensing layer overlaps the first driving electrode and the first sensing electrode, and gaps exist between the first force sensing layer and the first driving electrode and between the first force sensing layer and the first sensing electrode.