Force Sensing in Touch Displays Using Stiffener Substrates
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Solution Overview
Problem
Existing methods for measuring force behind display modules like LCD, OLED, and e-ink suffer from hysteresis and drift effects due to non-rigid attachment of capacitive sensors, and foam layers introduce short-term drift issues.
Innovation Solution
A display device with a stiffener substrate attached to the frame, where force sensing elements are placed on the stiffener substrate, allowing it to deflect in sync with the display substrate, reducing hysteresis and drift by transmitting force effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a capacitive sensor is attached to an optical layer to measure force, then force measurement is enabled, but hysteresis and drift effects occur due to non-rigid attachment
Solution Approach 1:
A stiffener substrate is introduced as an intermediary component between the display module and the force sensor. This stiffener substrate is rigidly secured to the display module's optical layers while providing a stable mounting surface for the force sensor, thereby eliminating the non-rigid attachment that causes hysteresis and drift effects.
Solution Approach 2:
The force sensing system is segmented into distinct functional components: the display module, the stiffener substrate, and the force sensor. This segmentation allows the stiffener substrate to specifically address the attachment rigidity issue without affecting the other components, isolating the solution to the precise problem area.
2Reliability
If a foam layer is added between the capacitive sensor and ground to improve mounting, then sensor attachment is enhanced, but short term drift effects are introduced
Solution Approach 1:
The foam layer that causes drift effects is completely removed from the system. Instead of using foam for mounting, the invention employs a rigid stiffener substrate that provides stable attachment without introducing the compliant, drift-inducing characteristics of foam material.
3Reliability
If the optical layer is made more rigid to reduce deflection, then hysteresis is reduced, but the display module becomes more complex
Solution Approach 1:
Rather than modifying the optical layers in the existing display module structure, the solution adds a new dimension by introducing a stiffener substrate as a separate mounting platform. This approach achieves the desired rigidity without altering or complicating the original optical layer construction.
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 enables accurate force measurement by ensuring the force sensor moves in sync with the input surface, reducing hysteresis and drift effects, thereby improving the usability and reliability of force sensing in display modules.
Implementation Method 1
A first force sensing element is disposed on the stiffener substrate... A second force sensing element is provided, wherein a distance between the first force sensing element and the second force sensing element decreases when the display substrate is deflected
Data Source
AI summary
Embodiments described herein include a display device that includes a display substrate coupled to a frame. A stiffener substrate is also coupled to the frame. A first force sensing element is disposed on the stiffener substrate, and the stiffener substrate is disposed between the first force sensing element and the display substrate. The display device also includes a second force sensing element, where a distance between the first force sensing element and the second force sensing element decreases when the display substrate is deflected.