Thin Double-Faced PSA Sheet Balancing Processability and Impact Resistance
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Solution Overview
Problem
Existing double-faced pressure-sensitive adhesive (PSA) sheets face a trade-off between processability and impact resistance, with PET support substrates compromising impact resistance and substrate-free sheets lacking in processability, especially in thin applications for portable electronic devices.
Innovation Solution
A double-faced PSA sheet with a total thickness of 60 μm or less, featuring a middle layer made of a water-dispersed material with a Young's modulus of 1.5 MPa to 1500 MPa, and PSA layers formed from water-dispersed compositions, ensuring minimal interlayer component migration and improved adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a PET support substrate is used in a double-faced PSA sheet, then processability is improved, but impact resistance deteriorates
Solution Approach 1:
The patent removes the PET support substrate entirely, creating a substrate-free PSA sheet structure consisting only of adhesive layers. This extraction eliminates the high-elasticity substrate that causes poor impact resistance while maintaining processability through alternative means (proper adhesive layer design and thickness control).
Solution Approach 2:
The patent creates a composite structure with multiple adhesive layers of different formulations. The first adhesive layer has different properties than the second adhesive layer, allowing optimization of each layer's function - one layer provides bonding while the other provides impact resistance, achieving both requirements without a substrate.
2Strength
If a substrate-free PSA sheet is used to improve impact resistance, then impact resistance is improved, but processability deteriorates
Solution Approach 1:
The patent divides the adhesive system into multiple separate adhesive layers instead of using a single-layer substrate-free sheet. This segmentation allows each layer to perform specific functions - one layer optimized for processing stability while another provides impact resistance - thereby improving processability while maintaining impact resistance.
3Strength
If the PSA layer thickness is increased to improve impact resistance, then impact resistance is improved, but the sheet becomes too thick for thin portable electronic devices
Solution Approach 1:
The patent uses a composite multi-layer adhesive structure where each layer is relatively thin but the combination provides enhanced impact resistance. This allows achieving the required mechanical strength without increasing the total thickness beyond acceptable limits for portable electronic devices.
Solution Approach 2:
The patent changes the physical and chemical parameters of the adhesive layers, including viscosity, molecular weight, and composition ratios, to optimize the balance between impact resistance and thickness. By adjusting these parameters, the adhesive layers provide enhanced mechanical properties without requiring increased thickness.
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 sheet achieves both good processability and impact resistance, suitable for bonding components in portable electronic devices, with enhanced peel strength and reliability.
Implementation Method 1
By using a water-dispersed material (specifically, a water dispersion of middle-layer-forming materials) as the middle-layer-forming material, it is possible to prevent or reduce migration of components that may occur at the interfaces with the PSA layers.
Implementation Method 2
pressure-sensitive adhesive (PSA) exists as a soft solid (a viscoelastic material) in a room temperature range and has a property to adhere easily to adherend with some pressure applied
Data Source
AI summary
A thin double-faced PSA sheet capable of combining processability and impact resistance is provided. Provided is a double-faced PSA sheet having a first PSA layer, at least one middle layer, and a second PSA layer in this order. The double-faced PSA sheet has a total thickness of 60 μm or less. The middle layer has a thickness accounting for 10% to 60% of the total thickness, is formed from a water-dispersed material, and has a Young's modulus in the range of 1.5 MPa to 1500 MPa.