Transfer Foil for Touch Sensor Electrode Formation
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Solution Overview
Problem
Existing touch sensors face challenges in forming detection electrodes on thin supports without breaking, especially when transferring the detection electrode to a support, and in preventing external connection terminals from cracking during thermocompression bonding.
Innovation Solution
A transfer foil with a temporary support, a conductive layer, and a pressure-sensitive or curable adhesive layer is used, where the peel adhesion between the temporary support and the conductive layer is minimized, and the adhesive layer has a high modulus of elasticity and appropriate rubber content to ensure stable transfer and flexibility, preventing the detection electrode and external connection terminal from breaking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a thin support is used to make the touch sensor thin and flexible, then the flexibility is improved, but it becomes difficult to handle the support and to stably form the detection electrode on the support
Solution Approach 1:
The invention divides the support structure into two segments: a thin support (for flexibility) and a temporary support (for stability during manufacturing). The detection electrode is first formed on the temporary support, then transferred to the thin support. This segmentation allows each component to fulfill its specific function without compromise.
Solution Approach 2:
The temporary support acts as an intermediary carrier that enables stable formation and handling of the detection electrode during the manufacturing process. It mediates between the need for thinness/flexibility and the need for stability during electrode formation, allowing the electrode to be safely transferred to the thin support afterward.
2Adaptability or versatility
If the detection electrode is transferred to a thin support, then the touch sensor becomes thinner and more flexible, but the fine metal wire forming the detection electrode is easily broken
Solution Approach 1:
The detection electrode is formed on the temporary support before transfer, allowing the fine metal wire to be established in a stable environment. The temporary support provides a robust platform for electrode formation, and the peeling process is performed after the electrode is fully formed, minimizing the risk of breaking during the most vulnerable phase.
Solution Approach 2:
The temporary support serves as a cushioning platform that protects the fragile fine metal wire during the formation process. By providing a stable, easy-to-handle support during electrode creation, it prevents breakage before the transfer occurs, cushioning the vulnerable electrode from mechanical stress.
3Reliability
If external connection terminal is connected to flexible print substrate by thermocompression, then electrical connection is achieved, but the support bends and external connection terminal is excessively displaced causing cracks
Solution Approach 1:
The external connection terminal is positioned and fixed on the temporary support before the thermocompression bonding process. This preliminary positioning ensures that when thermocompression is applied, the terminal is already in the correct position and the support structure is prepared to minimize bending, preventing excessive displacement and cracks.
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 allows for the successful transfer of detection electrodes to thin supports without breaking and prevents external connection terminals from cracking during thermocompression, ensuring the flexibility and reliability of touch sensors on flexible displays.
Implementation Method 1
a layer to be bonded to a support that is disposed on a surface of the conductive layer and consists of a pressure-sensitive adhesive layer or a curable adhesive layer
Implementation Method 2
a layer to be bonded to a support that is disposed on a surface of the conductive layer and consists of a pressure-sensitive adhesive layer or a curable adhesive layer
Implementation Method 3
the adhesive layer has a high modulus of elasticity and appropriate rubber content to ensure stable transfer and flexibility
Data Source
AI summary
A transfer foil for a touch sensor includes a temporary support, a conductive layer, and a layer to be bonded to a support. The peel adhesion between the temporary support and the conductive layer is 0.20 N/mm or less. The layer to be bonded to a support has a thickness of 20 μm or less, and a modulus of elasticity of 0.10 MPa or more at a temperature of 130° C. The conductive layer includes a detection electrode that has a mesh pattern formed of a thin wire consisting of a conductive member and an external connection terminal that consists of a conductive member and is drawn from the detection electrode. The thin wire forming the mesh pattern of the detection electrode has a line width of 1 μm or more and 4.5 μm or less.