Piezoelectric Sensor Orientation for Touch Sensitivity
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Solution Overview
Problem
Conventional displacement detection sensors in touch input devices, such as those used in mobile terminals, suffer from low pressing detection sensitivity due to the use of protective films and glass surfaces, which reduce the effectiveness of pressure-sensitive sensors.
Innovation Solution
A displacement detection sensor utilizing a flat-film piezoelectric sensor with a chiral polymer, specifically polylactic acid, where the macro direction of tensile stresses and molecular orientation intersect at approximately 45°, enhancing electric charge generation and sensitivity, and multiple sensors are mounted on a plate member to increase signal amplitude without cancellation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective film and glass surface are used in touch input devices, then the device structure is protected and has good appearance, but the pressing detection sensitivity is reduced
Solution Approach 1:
The patent extracts the pressing detection function from the protective film and glass surface structure, placing a dedicated piezoelectric sensor between the operation surface and the protective film. This separates the protection function (handled by protective film and glass) from the detection function (handled by piezoelectric sensor), allowing both to perform optimally without interfering with each other.
Solution Approach 2:
The piezoelectric sensor acts as an intermediary element between the operation surface and the protective film/glass structure. It transduces the mechanical pressing force into electrical signals while being positioned in a location that allows it to detect pressing forces before they are attenuated by the protective film and glass surface.
2Device complexity
If linear electrodes in a matrix are used to detect electric charge, then the device structure is simple, but the pressing detection sensitivity is low
Solution Approach 1:
The patent changes the electrode configuration from linear matrix electrodes to ring-shaped electrodes with multiple segments. This geometric parameter change increases the electrode surface area and optimizes the electric field distribution, thereby improving the detection sensitivity of electric charge generated by pressing without significantly increasing device complexity.
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
The solution significantly improves pressing detection sensitivity while maintaining a thin and transparent design, ensuring high sensitivity and good appearance without relying on the ambient environment.
Implementation Method 1
a flat-film piezoelectric sensor mounted on the other principal plane of the plate member and including a flat piezoelectric film and detection electrodes formed on both principal planes of the piezoelectric film
Implementation Method 2
The piezoelectric film contains a chiral polymer. The piezoelectric sensor is mounted on the plate member so that a macro direction of tensile stresses generated in the piezoelectric sensor by the plate member pressed from the one principal plane in the bonding region of the piezoelectric sensor and a molecular orientation direction of the chiral polymer intersect each other
Data Source
AI summary
A displacement detection sensor has a plate member and piezoelectric sensors with a piezoelectric film of PLLA. The piezoelectric sensors are mounted on the face of the plate member on the opposite side of the operation surface thereof. Tensile stresses are generated in the entire face of the plate member at pressing the operation surface. The piezoelectric sensor is mounted so that the direction of macro tensile stress in the plate member in the region in which the piezoelectric sensor is mounted and molecular orientation direction of the piezoelectric film intersect each other at an angle of 45°. The piezoelectric sensor is mounted so that the direction of macro tensile stress in the plate member in the region in which the piezoelectric sensor is mounted and molecular orientation direction of the piezoelectric film intersect each other at an angle of approximately 45°.