Piezoelectric Pressing Sensor Placement to Prevent Display Color Distortion
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Solution Overview
Problem
Conventional electronic devices with thin display panels and piezoelectric pressing sensors suffer from color changes due to double refractivity, leading to undesired image color when the pressing sensor is integrated between polarization plates, affecting both transmissive and reflective types.
Innovation Solution
A display panel structure with a piezoelectric film made of uniaxially stretched chiral polymer, such as polylactic acid, is positioned on the opposite side of the front polarization plate, allowing light to pass through the piezoelectric film without altering the image color, and is spaced from the display panel to prevent damage and maintain sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a piezoelectric element such as a chiral polymer is used to detect pressing amount, then pressing detection capability is improved, but double refractivity causes color change and degrades image quality
Solution Approach 1:
The pressing sensor is extracted from the conventional position between the liquid crystal panel and front polarization plate, and placed on the opposite side of the front polarization plate. This extraction removes the harmful double refractivity effect from the light transmission path while preserving the pressing detection function.
Solution Approach 2:
The front polarization plate serves as an intermediary element that separates the pressing sensor from the light transmission path. Light passes through the polarization plate first, then through the pressing sensor, which acts as a mediator that detects pressing without affecting the already-polarized light's color properties.
2Device complexity
If the pressing sensor is arranged between the front and back polarization plates, then integration is improved, but light must pass through the piezoelectric element causing color distortion
Solution Approach 1:
The pressing sensor is extracted from the conventional integrated position between polarization plates and relocated to the opposite side of the front polarization plate. This maintains functional integration while eliminating the harmful optical effect.
Solution Approach 2:
Instead of placing the pressing sensor before the front polarization plate in the light path, the sensor is inverted to the opposite side, reversing the conventional arrangement. This inversion allows light to pass through the polarization plate first, preventing color distortion.
3Power
If the piezoelectric film is made of uniaxially stretched chiral polymer, then piezoelectric properties are improved, but double refractivity with different refractive indices causes retardation characteristic
Solution Approach 1:
The piezoelectric film with double refractivity is extracted from the light transmission path by positioning it on the opposite side of the front polarization plate. This maintains the piezoelectric response capability while removing the harmful retardation effect from the optical path.
Solution Approach 2:
The uniaxially stretched chiral polymer is used specifically in the pressing sensor region where piezoelectric properties are needed, while the front polarization plate maintains its optical properties in the light transmission path. Each component has optimized local quality for its specific function.
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 configuration enables accurate detection of pressing amounts while maintaining the desired image color and preventing damage to the polarization plates, ensuring high sensitivity and temperature stability of the pressing sensor.
Implementation Method 1
the pressing sensor has a piezoelectric film formed of a chiral polymer
Implementation Method 2
a wave vibrated in the direction parallel to the stretching direction of uniaxially stretched poly-L-lactic acid (PLLA) has a refractive index of 1.47. On the other hand, a wave vibrated in the direction perpendicular to the stretching direction of uniaxially stretched poly-L-lactic acid (PLLA) has a refractive index of 1.45
Implementation Method 3
the front and back polarization plates transmit only a wave (light wave) vibrated in a particular direction
Data Source
AI summary
An electronic device with pressing input function has a substantially rectangular parallelepiped housing. In the housing, a pressing sensor, a display panel, a protection member, and a computation circuit module are arranged. In the display panel, a polarization plate is arranged on a first side of a liquid crystal panel. In the pressing sensor, electrodes are formed on both planar faces of a piezoelectric film having double refractivity. The pressing sensor is arranged on the operation surface (the display face) side of the housing relative to the front polarization plate.