Capacitive Sensor Adhesive Peeling Mitigation
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Solution Overview
Problem
Capacitive touch panels with glass substrates and protective substrates experience adhesive layer peeling due to differential expansion and contraction caused by temperature changes, leading to shearing forces that existing adhesive layers cannot effectively absorb.
Innovation Solution
Incorporating an intermediate layer with a translucent property between the resinous panel and the sensor substrate, with two adhesive layers on either side of the intermediate layer, allowing independent deformation and absorption of shearing forces, thereby stabilizing the adhesive layers and preventing peeling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single adhesive layer is used between the protective substrate and sensor substrate, then the structure is simple, but the adhesive layer peels off due to shearing force from differential thermal expansion
Solution Approach 1:
The single adhesive layer is segmented into two separate adhesive layers by introducing an intermediate layer. This segmentation allows each adhesive layer to independently accommodate thermal expansion differences, preventing peeling while maintaining structural simplicity through modular design.
Solution Approach 2:
An intermediate layer with translucent property is introduced as a mediator between the protective substrate and sensor substrate. This intermediate layer absorbs differential thermal expansion stresses, preventing them from transferring to the adhesive layers and causing peeling, while maintaining optical performance.
2Reliability
If the adhesive force of the adhesive sheet is increased to prevent peeling, then the adhesive layer stability improves, but the device complexity increases
Solution Approach 1:
The intermediate layer acts as a stress-absorbing mediator that eliminates the need for high adhesive forces. By capturing thermal expansion differences within the intermediate layer itself, the adhesive layers only need to perform their basic bonding function, simplifying the overall system requirements.
3Reliability
If the adhesive sheet is made more flexible to absorb shearing force, then the adhesive layer stability improves, but the manufacturing precision decreases
Solution Approach 1:
The intermediate layer serves as a dedicated component to absorb shearing forces through its material properties, allowing the adhesive layers to maintain their standard manufacturing specifications. This separation of functions preserves manufacturing precision while achieving the needed flexibility for thermal accommodation.
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 intermediate layer and dual adhesive layers effectively mitigate shearing forces caused by temperature changes and external forces, reducing the stress on the adhesive layers and preventing peeling, while maintaining optical performance.
Implementation Method 1
when environment temperature around the capacitive sensor changes, the resinous panel and glass base material expand or contract in different directions
Implementation Method 2
a shearing force is exerted on the adhesive sheet placed between the protective substrate and the capacitive touch panel sensor
Implementation Method 3
a first adhesive layer that bonds the panel and intermediate layer together is provided between the panel and the intermediate layer
Data Source
AI summary
A capacitive sensor includes: a resinous panel that has a translucent property, a main surface of the panel being a manipulation surface; a sensor substrate placed so as to face another main surface of the panel, the other main surface being opposite to the manipulation surface of the panel, the sensor substrate having a glass base material and a transparent electrode provided on at least one main surface of the base material; an intermediate layer that has a translucent property, the intermediate layer being disposed between the panel and the sensor substrate; a first adhesive layer disposed between the panel and the intermediate layer, the first adhesive layer bonding the panel and the intermediate layer together; and a second adhesive layer disposed between the sensor substrate and the intermediate layer, the second adhesive layer bonding the sensor substrate and the intermediate layer together.