Solvent-Free Acrylic Adhesive for Flexible Displays
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Solution Overview
Problem
Conventional adhesive layers for mobile devices face challenges in achieving a balance between adhesive strength, bending durability, and moist heat haze resistance, particularly when exposed to curved and flexible display requirements.
Innovation Solution
An adhesive layer formed by curing an acrylic resin-containing composition with specific properties, including at least two acrylic resins having different glass transition temperatures and a hydroxyl-containing monomer like 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate, which provides excellent adhesive strength, bending durability, and moist heat haze resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a solvent-containing acrylic adhesive agent is used for thicker coating application, then the adhesive layer can achieve sufficient thickness for impact-absorbing property, but the coating liquid is liable to drip during application and solvent evaporation is difficult, resulting in foaming of the adhesive layer
Solution Approach 1:
The patent changes the physical state parameter of the adhesive agent from solvent-containing to solvent-free, eliminating the drying step and preventing foaming while enabling thick coating application without dripping issues
Solution Approach 2:
The patent extracts and removes the solvent component from the adhesive agent formulation, leaving only the acrylic resin and crosslinking agents, which eliminates solvent evaporation problems and foaming while maintaining coating applicability
2Duration of action of stationary object
If the adhesive agent has a lower elastic modulus to improve bending durability, then the adhesive layer can withstand repeated bending, but the adhesive strength and moist heat haze resistance deteriorate
Solution Approach 1:
The patent changes the chemical composition parameters by selecting specific acrylic resins with particular glass transition temperatures and molecular weights, and by using specific crosslinking agents, achieving a balanced elastic modulus that provides both bending durability and adhesive strength
Solution Approach 2:
The patent creates a composite adhesive system combining acrylic resins with crosslinking agents, where the crosslinking network provides structural integrity and adhesive strength while the acrylic resin matrix provides flexibility and bending durability
3Ease of operation
If a commonly available conventional solvent-containing acrylic adhesive agent is used, then the adhesive layer can be applied easily, but the solvent is liable to cause foaming and the adhesive layer suffers from poor bending durability and moist heat haze resistance
Solution Approach 1:
The patent changes the chemical composition by using solvent-free acrylic resin with specific molecular weight and glass transition temperature parameters, eliminating solvent-related foaming and improving moist heat haze resistance while maintaining ease of application
Solution Approach 2:
The patent replaces the solvent evaporation mechanism with a crosslinking curing mechanism, where the adhesive cures through chemical crosslinking rather than solvent evaporation, eliminating foaming and improving reliability in moist heat environments
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 adhesive layer demonstrates an adhesive strength of not less than 25 N/25 mm, bending durability of over 100,000 times, and moist heat haze resistance of not greater than 1.0%, making it suitable for flexible and foldable smartphone applications.
Implementation Method 1
active energy radiation-curable adhesive agent
Implementation Method 2
adhesive composition containing an acrylic resin and a crosslinking agent
Data Source
AI summary
An adhesive layer is formed by curing an adhesive composition [I] containing an acrylic resin (X), and has an adhesive strength (α) of not less than 25 N/25 mm, a bending durability (β) of not less than 100,000 times, and a moist heat haze resistance (γ) of not greater than 1.0% as measured under predetermined conditions. The adhesive layer has excellent adhesive strength to adherends, excellent bending durability, and excellent moist heat haze resistance.