Flexible Foldable Display Ultrasonic Fingerprint Adhesive Layer
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Solution Overview
Problem
Existing flexible foldable display technologies face challenges in effectively transmitting ultrasonic waves due to the presence of air gaps in foam materials used for vibration damping, which hinders the performance of under-screen fingerprint identification systems.
Innovation Solution
A flexible foldable display module is designed with an adhesive layer comprising a stacked structure of optically clear adhesive and pressure sensitive adhesive layers, sandwiched between a display substrate and a support plate, ensuring a dense structure that minimizes air gaps and enhances the transmission of ultrasonic waves, while the support plate's varying thicknesses and a depression structure accommodate a fingerprint sensor for improved signal transmission and structural support.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If foam materials are used for vibration damping, then vibration damping performance is improved, but ultrasonic wave transmission is hindered due to air gaps
Solution Approach 1:
The patent removes the foam material with air gaps from the fingerprint sensor region and replaces it with a dense adhesive layer structure. This extracts the harmful air-filled foam while maintaining vibration damping through alternative means (the multi-layer adhesive structure), thereby eliminating the barrier to ultrasonic wave transmission.
Solution Approach 2:
The patent changes the physical parameters of the adhesive layer by creating a multi-layer stacked structure with specific thickness ratios. The first adhesive layer has thickness of 0.2-0.34 times the second adhesive layer, creating a dense configuration that maintains vibration damping while enabling ultrasonic transmission, thus changing the density and structural parameters to resolve the contradiction.
2Reliability
If a dense adhesive layer is used to transmit ultrasonic waves, then ultrasonic wave transmission is improved, but vibration damping may be reduced
Solution Approach 1:
The patent employs a composite multi-layer adhesive structure consisting of two different adhesive layers with specific thickness ratios. This composite structure combines the vibration damping properties of thicker adhesive material with the ultrasonic transmission capabilities of the optimized dense configuration, achieving both functions simultaneously.
3Reliability
If the support plate thickness is reduced over the fingerprint region, then ultrasonic wave transmission is improved, but structural support is weakened
Solution Approach 1:
The support plate is designed with non-uniform thickness, having a first portion with thickness of 30-50 μm over the fingerprint identification region and a second portion with greater thickness elsewhere. This local quality variation provides thin regions for ultrasonic transmission while maintaining structural support through thicker regions, resolving the contradiction between transmission and support.
4Strength
If multiple adhesive layers are stacked, then vibration damping and adhesion are improved, but device complexity increases
Solution Approach 1:
The adhesive layer is segmented into two distinct layers with different thicknesses and functions. The first adhesive layer (thinner, 0.2-0.34 times the second layer's thickness) provides ultrasonic transmission, while the second adhesive layer (thicker) provides vibration damping and structural adhesion. This segmentation allows each layer to optimize its function while together resolving the contradiction between performance and 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 enables efficient ultrasonic wave transmission and effective fingerprint identification, preventing local collapse and ensuring high transmission efficiency and response sensitivity, while maintaining structural integrity and light transmittance for optical fingerprint sensors.
Implementation Method 1
the presence of air gaps in foam materials used for vibration damping, which hinders the performance of under-screen fingerprint identification systems
Implementation Method 2
The first adhesive layer includes at least one of an optically clear adhesive or a pressure sensitive adhesive
Data Source
AI summary
A flexible foldable display module includes a display substrate having a fingerprint identification region, a flexible cover plate disposed on a side of a display surface of the display substrate, a support plate located on a side of the display substrate away from the display surface thereof, and an adhesive layer located between the support plate and the display substrate. The support plate includes a first portion and a second portion other than the first portion. The first portion covers at least the fingerprint identification region. A thickness of the first portion is less than a thickness of the second portion, and a surface of the first portion proximate to the display substrate is flush with a surface of the second portion proximate to the display substrate. The adhesive layer includes a first adhesive layer, a first base layer, and a second adhesive layer that are sequentially stacked.