Touch Sensor Panel PSA Adhesive Layers for Dynamic Folding
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Solution Overview
Problem
Conventional touch sensor panels face challenges in suppressing cracks in the electrode layer due to high modulus values of UV adhesives, which hinder dynamic folding capability and thickness optimization.
Innovation Solution
The use of pressure-sensitive adhesive (PSA) layers with a modulus of 0.2 to 2 and thickness of 10 to 30 μm between the base, electrode, and functional layers, comprising a COP base layer, PSA adhesive layers, and a polarization layer, to enhance dynamic folding capability and prevent cracks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If UV adhesive is used to bond the COP layer and electrode layer, then bonding strength is improved, but the modulus becomes too high (2.5 or more) and thickness cannot be maintained at 5 μm or more
Solution Approach 1:
The patent changes the material parameter (modulus) of the adhesive layer from UV adhesive (modulus ≥ 2.5) to pressure-sensitive adhesive (modulus 0.2 to 2.0). This parameter change allows the adhesive to maintain bonding strength while achieving the required low modulus for dynamic folding capability, enabling the touch sensor panel to be folded without cracking the electrode layer.
2Strength
If UV adhesive is used with high modulus, then bonding strength is improved, but cracks occur in the electrode layer during dynamic folding
Solution Approach 1:
The patent changes the modulus parameter of the adhesive from UV adhesive (≥2.5) to pressure-sensitive adhesive (0.2 to 2.0). This parameter change enables the adhesive layer to flex during dynamic folding without transmitting excessive stress to the electrode layer, thereby preventing cracks while maintaining bonding strength.
3Adaptability or versatility
If adhesive thickness is increased to 5 μm or more, then dynamic folding capability is improved, but UV adhesive cannot achieve this thickness
Solution Approach 1:
The patent changes the material type from UV adhesive to pressure-sensitive adhesive, which has different physical properties. This change enables the adhesive to be applied at a thickness of 5 μm or more while maintaining manufacturability, as pressure-sensitive adhesive can be coated and cured without the strict thickness limitations of UV adhesive.
4Adaptability or versatility
If modulus is lowered to improve dynamic folding capability, then crack resistance is improved, but bonding strength may be reduced
Solution Approach 1:
The patent changes the material from UV adhesive to pressure-sensitive adhesive with modulus of 0.2 to 2.0. This parameter change achieves the counterintuitive result of maintaining bonding strength while lowering modulus, because pressure-sensitive adhesive has different adhesive mechanisms that compensate for the lower modulus.
Solution Approach 2:
The patent uses pressure-sensitive adhesive as a composite material solution that combines the properties of low modulus (for flexibility) with adequate bonding strength (for adhesion). This composite approach allows the adhesive layer to serve multiple functions simultaneously.
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
This configuration effectively lowers the modulus to 2.5 or less, maintains thickness at 5 μm or more, and maximizes dynamic folding capability while minimizing thickening and crack occurrence in the electrode layer.
Implementation Method 1
One side of the first adhesive layer may be bonded to one side of the base layer. The first adhesive layer may be composed of a pressure-sensitive adhesive (PSA). One side of the electrode layer may be bonded to the other side of the first adhesive layer.
Data Source
AI summary
A touch sensor panel includes a base layer, a first adhesive layer having one side bonded to one side of the base layer and composed of a pressure-sensitive adhesive (PSA), an electrode layer having one side bonded to the other side of the first adhesive layer, a second adhesive layer having one side bonded to the other side of the electrode layer and composed of a pressure-sensitive adhesive (PSA), and a functional layer having one side bonded to the other side of the second adhesive layer.