Optical Adhesive Sheet UV Curing and Swelling Control
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Solution Overview
Problem
Optical adhesive sheets used in image display devices, such as bezels, face challenges with low repulsion resistance and swelling rates, leading to issues like lifting, bubbles, and detachment under high temperature and humidity conditions due to inadequate solvent impregnation and flexibility.
Innovation Solution
An optical adhesive sheet with an adhesive agent layer formed by curing a composition of ethylhexyl acrylate and isobornyl acrylate using UV light with a UV intensity of 6 to 8 mW/cm² at 20 to 30°C, achieving a swelling rate of 60% or more, and including a photoinitiator, which improves cross-linking density and flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional acrylic adhesive agents are used in optical adhesive sheets, then the sheets can be manufactured with standard adhesive properties, but the repulsion resistance and swelling rate are insufficient, leading to lifting, bubbles, and detachment under high temperature and humidity conditions
Solution Approach 1:
The patent changes the chemical composition parameters of the adhesive agent by using a specific acrylic copolymer with controlled swelling rate (60-90%) and molecular weight (500,000-2,000,000), along with optimized photoinitiator content (0.3-0.5 part by weight), to achieve both high repulsion resistance and manufacturability
Solution Approach 2:
The patent creates a composite adhesive system combining acrylic copolymer, photoinitiator, and specific monomers (ethylhexyl acrylate and isobornyl acrylate) to achieve properties that neither component could provide alone, particularly the balance between swelling rate and repulsion resistance
2Reliability
If the adhesive layer has low swelling rate, then the manufacturing process is simpler, but the flexibility and solvent impregnation are insufficient, causing poor repulsion resistance under high temperature and humidity
Solution Approach 1:
The patent optimizes the swelling rate parameter to a specific range (60-90%) through selection of acrylic copolymer with controlled molecular weight and composition, achieving sufficient flexibility and solvent impregnation while maintaining compositional stability
Solution Approach 2:
The patent creates a porous structure in the adhesive layer through controlled swelling, allowing solvent impregnation and improving flexibility, while the cross-linked network maintains structural integrity
3Productivity
If UV curing is performed with high intensity, then the curing speed is faster, but the swelling rate decreases below 60%, reducing repulsion resistance and causing detachment issues
Solution Approach 1:
The patent changes the UV curing parameters to use moderate intensity (6-8 mW/cm²) with extended exposure time, achieving both adequate curing speed and high swelling rate (60-90%) for optimal repulsion resistance
Solution Approach 2:
The patent makes the curing process dynamic by adjusting UV intensity and exposure time based on the desired swelling rate, allowing optimization of both curing speed and adhesive performance
4Reliability
If the adhesive agent composition includes high molecular weight acrylic copolymer, then the repulsion resistance improves, but the curing conditions become more difficult to control
Solution Approach 1:
The patent changes the molecular weight parameter of the acrylic copolymer to a specific range (500,000-2,000,000) and adjusts corresponding curing parameters (UV intensity 6-8 mW/cm², exposure time for 1500 mJ/cm² total dose) to achieve optimal repulsion resistance while maintaining controllable curing
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 provides enhanced repulsion resistance and durability by ensuring sufficient solvent impregnation in the adhesive layer, maintaining bonding properties and preventing bubbles and detachment, even under high temperature and humidity conditions.
Implementation Method 1
the adhesive agent layer is formed by curing an adhesive agent composition, which includes an acrylic copolymer formed by polymerizing a monomer mixture including ethylhexyl acrylate and isobornyl acrylate, at an ambient temperature of 20 to 30° C. by irradiation with UV light
Data Source
AI summary
An optical adhesive sheet having an excellent repulsion resistance and an excellent swelling rate, and a method for manufacturing the same.