Piezoelectric Element Positioning in Display Devices
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Solution Overview
Problem
Existing display devices with piezoelectric elements disposed on the outer peripheral portion of touch panels face difficulties in detecting minute displacements due to noise interference and adverse effects on display performance.
Innovation Solution
The piezoelectric element is positioned below the backlight unit, with the light source and reflector interposed between the piezoelectric element and the display, and in OLED configurations, a light shielding member is used between the display and the piezoelectric element to eliminate noise influence and maintain display performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the piezoelectric element is disposed on the outer peripheral portion of the touch panel, then the structure is simple, but it is difficult to detect minute displacement in the normal direction of the operation surface
Solution Approach 1:
The piezoelectric element is repositioned from the outer peripheral portion to the back surface of the operation surface, changing the spatial dimension of detection. This allows the element to detect normal direction displacement (perpendicular to the surface) rather than lateral displacement, thereby enabling minute displacement detection while maintaining structural simplicity.
2Measurement precision
If the piezoelectric element is provided between the back surface of the operation surface and the touch panel, then minute displacement can be detected, but noise from the touch panel or display portion affects the piezoelectric element
Solution Approach 1:
A light shielding member is introduced as an intermediary component between the display portion and the piezoelectric element. This member blocks noise (light and electromagnetic interference) from the display portion while allowing the mechanical displacement detection function to operate, thus protecting the piezoelectric element without compromising its detection capability.
3Measurement precision
If the piezoelectric element is provided between the back surface of the operation surface and the touch panel, then minute displacement can be detected, but the piezoelectric element affects display performance of the display portion
Solution Approach 1:
The light shielding member serves as a mediator that separates the piezoelectric element from the display portion. It prevents the piezoelectric element from interfering with light transmission and display performance while maintaining the element's position for effective displacement detection, thus resolving the conflict between detection precision and display quality.
4Object-affected harmful factors
If a light shielding member is added between the display and piezoelectric element, then noise influence is eliminated, but device complexity increases
Solution Approach 1:
The light shielding member is designed to perform multiple functions simultaneously: it blocks noise from the display portion, provides structural support, and maintains the positional relationship between components. By consolidating multiple functions into a single component, the design minimizes the increase in device complexity while achieving effective noise shielding.
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 arrangement effectively blocks noise from the display and ensures accurate detection of pressing forces without affecting the display performance, allowing for precise detection of minute displacements and improved sensitivity.
Implementation Method 1
a piezoelectric element located below the light source for detecting a pressing force applied to the operation panel
Implementation Method 2
a reflector located below the light source for reflecting light emitted by the light source toward the display
Data Source
AI summary
A display device includes a display portion, a light source, a reflecting member, and a piezoelectric element. The display portion displays an image. The light source outputs light to the display portion. The reflecting member is provided on one side of a principal surface of the display portion and reflects the light of the light source. The piezoelectric element is provided on one side of the principal surface of the reflecting member.