Dual-Layer Touch Module Adhesive Dielectric Constant Optimization
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Solution Overview
Problem
Metal nanowire touch devices face reliability issues due to high moisture intrusion, leading to electro-migration and potential short circuits, as materials with high dielectric constants used for optical adhesive layers enhance water absorptivity.
Innovation Solution
A touch module with two optically transparent adhesive layers, where the first layer has a dielectric constant between 1.5 and 3.0 and the second layer between 3.0 and 8.0, reducing moisture intrusion and maintaining high capacitance, thereby slowing down electro-migration and ensuring product reliability and sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If materials with high dielectric constant are used for the optical adhesive layer to meet high capacitance requirements, then touch sensitivity is improved, but water absorptivity increases leading to moisture intrusion and electro-migration of metal nanowires
Solution Approach 1:
The optical adhesive layer is divided into two separate layers: a first optical adhesive layer with low dielectric constant (1.5-3.0) that provides moisture barrier function, and a second optical adhesive layer with high dielectric constant (3.0-8.0) that provides capacitance enhancement. This segmentation allows each layer to perform its specific function without compromising the other, resolving the contradiction between moisture resistance and touch sensitivity.
Solution Approach 2:
Different regions of the adhesive structure are assigned different dielectric constants based on their functional requirements. The first adhesive layer near the metal nanowires uses low dielectric constant material to prevent moisture intrusion and electro-migration, while the second adhesive layer uses high dielectric constant material to enhance capacitance and touch sensitivity. This local differentiation optimizes both reliability and performance.
2Reliability
If a single optical adhesive layer with high dielectric constant is used to achieve high capacitance, then touch sensitivity is improved, but water absorptivity increases causing reliability issues
Solution Approach 1:
The adhesive system is segmented into two layers with distinct dielectric constant ranges. The first layer (dielectric constant 1.5-3.0) serves as a moisture barrier to ensure reliability, while the second layer (dielectric constant 3.0-8.0) provides capacitance enhancement. This segmentation achieves high reliability without requiring complex multi-functional materials.
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 effectively prevents moisture intrusion, maintaining high touch sensitivity and reliability by adjusting the dielectric constants and thicknesses of the adhesive layers, ensuring resistance and optical properties within specified ranges even under harsh conditions.
Implementation Method 1
a dielectric constant of the first transparent adhesive layer is between 1.5 and 3.0
Implementation Method 2
materials with high dielectric constant generally have better water absorptivity
Implementation Method 3
a dielectric constant of the second transparent adhesive layer is between 3.0 and 8.0
Implementation Method 4
causing electro-migration of metal nanowires in the display or touch devices
Data Source
AI summary
A touch module includes a substrate, a touch sensing layer, a first transparent adhesive layer, and a second transparent adhesive layer. The substrate has a visible area and a peripheral area surrounding the visible area. The touch sensing layer is disposed on the substrate and located in the visible area. The first transparent adhesive layer is disposed on the touch sensing layer, and a dielectric constant of the first transparent adhesive layer is between 1.5 and 3.0. The second transparent adhesive layer is disposed on the first transparent adhesive layer, and a dielectric constant of the second transparent adhesive layer is between 3.0 and 8.0.