Piezoelectric Touch Panel with Discrete Electrodes
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Solution Overview
Problem
Current touch panels face challenges in detecting multi-touch and pressing force simultaneously while maintaining transparency, due to the need for extensive use of rare and costly transparent electrodes, complex signal processing, and impaired light transmittance from multiple layered structures.
Innovation Solution
A touch panel featuring a piezoelectric sheet with electrodes distributed discretely rather than covering the entire surface, using poly-L-lactic acid with oriented stretching axes, and employing a method to calculate pressing position and force by comparing voltages generated in each electrode set, allowing for efficient detection of both pen and finger inputs and multi-touch capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If transparent electrodes are used to maintain high transparency, then light transmittance is improved, but the cost increases due to use of rare materials like ITO
Solution Approach 1:
The patent divides the touch panel into multiple layers, with the piezoelectric sheet forming a distinct functional layer between the transparent electrode and the touch-sensitive surface. This segmentation allows the transparent electrode to be optimized for light transmittance while the piezoelectric layer handles the mechanical sensing, reducing the need for extensive use of expensive transparent electrode material across the entire panel surface.
Solution Approach 2:
The patent employs a composite structure combining a piezoelectric sheet (such as PVDF or P(VDF-TrFE)) with transparent electrode materials. This composite approach leverages the piezoelectric properties of the polymer sheet for force sensing while maintaining optical transparency through the electrode layer, achieving a cost-effective balance between performance and material cost.
2Adaptability or versatility
If multiple layered structures are used to detect both position and pressing force, then detection capability is improved, but light transmittance is impaired
Solution Approach 1:
The patent segments the detection functions into distinct layers: the transparent electrode layer handles positional detection through capacitance changes, while the piezoelectric sheet layer handles pressing force detection through mechanical deformation. This segmentation allows each layer to be optimized for its specific function with minimal thickness, reducing overall light blocking while maintaining dual detection capabilities.
Solution Approach 2:
The patent transitions from a two-dimensional capacitance-based touch detection to a three-dimensional structure incorporating a piezoelectric sheet with specific crystal orientations. This dimensional addition enables force sensing in the vertical dimension while maintaining the transparent electrode's optical function, achieving multi-functional detection without compromising light transmittance.
3Measurement precision
If a piezoelectric sheet with oriented stretching axes is used, then pressing force detection is improved, but manufacturing complexity increases
Solution Approach 1:
The patent utilizes the piezoelectric sheet's inherent anisotropic properties by controlling the stretching orientation during manufacturing. By adjusting the stretching parameters and crystal orientation, the piezoelectric coefficients are optimized for force detection in specific directions. This parameter control approach enables precise force detection while using standard manufacturing processes for polymer film production.
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 enables reliable detection of positional and pressing force information with reduced material usage for transparent electrodes, improved light transmissivity, and simplified signal processing, supporting multi-touch functionality and cost-effective production.
Implementation Method 1
a piezoelectric sheet formed of poly-L-lactic acid having a stretching axis oriented in a predetermined direction; and first and second electrodes that are opposed to each other, formed on first and second main surfaces opposed to each other of the piezoelectric sheet
Data Source
AI summary
A touch panel having a piezoelectric sheet with a first region and a second region, and a surface protection film bonded to the second region of the piezoelectric sheet with a non-curable adhesive. The non-curable adhesive has a larger elasticity than a material that bonds the first region of the piezoelectric sheet to the surface protection film.