Pressure-Sensitive Adhesive Layer with Regional Modulus Control
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Solution Overview
Problem
Existing pressure-sensitive adhesive layers in flexible devices, such as foldable or rollable devices, suffer from defects like lifting, peeling, and bubble generation due to inconsistent physical properties across different parts of the device, particularly near and away from the folding or rolling axis, and existing methods struggle to create significant differences in elastic modulus and creep strain rate effectively.
Innovation Solution
A pressure-sensitive adhesive layer with distinct first and second regions, formed from the same composition, featuring different storage elastic moduli and creep strain rates, achieved through controlled electromagnetic wave irradiation of an acrylic copolymer with specific monomer units and cross-linking agents, ensuring large differences in elastic modulus and creep strain rate while minimizing differences in peel force and recovery rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electromagnetic wave irradiation is used to create physical property differences in the pressure-sensitive adhesive layer, then regional physical property differentiation is achieved, but the difference in elastic modulus and creep strain rate between regions is limited and cannot be greatly increased
Solution Approach 1:
The patent applies local quality by creating distinct first and second regions within the pressure-sensitive adhesive layer, where each region has different physical properties (storage elastic modulus and creep strain rate) tailored to specific functional requirements. The first region has higher elastic modulus and lower creep strain rate for structural stability, while the second region has lower elastic modulus and higher creep strain rate for flexibility and stress relief during folding operations.
Solution Approach 2:
The patent employs composite materials by formulating the pressure-sensitive adhesive layer as a composite structure containing multiple types of polymers with different characteristics. Specifically, it combines polymers with high elastic modulus and low creep strain rate with polymers having lower elastic modulus and higher creep strain rate, creating a composite material system that exhibits both high and low physical property regions within a single layer.
2Ease of manufacture
If the pressure-sensitive adhesive layer has high elastic modulus and low creep strain rate for cuttability and workability, then cutting performance is improved, but the adhesive layer becomes prone to lifting, peeling, and bubble generation in folding parts
Solution Approach 1:
The patent applies local quality by creating distinct first and second regions within the pressure-sensitive adhesive layer, where each region has different physical properties (storage elastic modulus and creep strain rate) tailored to specific functional requirements. The first region has higher elastic modulus and lower creep strain rate for structural stability, while the second region has lower elastic modulus and higher creep strain rate for flexibility and stress relief during folding operations.
Solution Approach 2:
The patent segments the pressure-sensitive adhesive layer into functionally distinct regions - a first region optimized for cuttability and workability with high elastic modulus, and a second region optimized for folding durability with low elastic modulus and high creep strain rate. This segmentation allows each region to independently perform its specialized function without compromising the other.
3Reliability
If the pressure-sensitive adhesive layer has low elastic modulus and high creep strain rate for folding flexibility, then stress relief during folding is improved, but cuttability and workability deteriorate
Solution Approach 1:
The patent applies local quality by creating distinct first and second regions within the pressure-sensitive adhesive layer, where each region has different physical properties (storage elastic modulus and creep strain rate) tailored to specific functional requirements. The first region has higher elastic modulus and lower creep strain rate for structural stability, while the second region has lower elastic modulus and higher creep strain rate for flexibility and stress relief during folding operations.
Solution Approach 2:
The patent segments the pressure-sensitive adhesive layer into functionally distinct regions - a first region optimized for cuttability and workability with high elastic modulus, and a second region optimized for folding durability with low elastic modulus and high creep strain rate. This segmentation allows each region to independently perform its specialized function without compromising the other.
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 maintains large differences in elastic modulus and creep strain rate between regions, reducing defects like lifting and peeling, while maintaining consistent peel force and recovery rate, enhancing the performance and durability of the adhesive layer in flexible devices.
Implementation Method 1
a method of irradiating with electromagnetic waves only a partial region of a pressure-sensitive adhesive layer in the form that is crosslinked by irradiation of electromagnetic waves, such as ultraviolet rays, to induce physical property differences in the region irradiated with electromagnetic waves and other regions
Data Source
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AI summary
The present application provides a pressure-sensitive adhesive layer comprising at least first and second regions having different physical properties, wherein the difference in physical properties, such as an elastic modulus or creep strain rate is maintained relatively large for each region, and the difference in physical properties, such as a peel force or recovery rate is maintained relatively small for each region.