Optical Adhesive Composition Reducing Cure Shrinkage
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Solution Overview
Problem
Adhesive compositions for optical use face challenges in visibility degradation due to air layers in image display devices, with existing solutions like transparent acrylic products being difficult to apply and prone to bubble formation and high cure shrinkage, which affects dimensional stability and adhesion.
Innovation Solution
A composition combining monofunctional and polyfunctional urethane (meth)acrylate-based oligomers with specific weight ratios, along with hydroxy group-containing (meth)acrylate-based monomers and additives, that undergo photo-curing to minimize cure shrinkage and enhance adhesion and viscosity control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a transparent acrylic cured product is used to fill the air layer, then visibility is improved, but the adhesive is difficult to apply and prone to bubble formation
Solution Approach 1:
The patent changes the physical and chemical parameters of the adhesive composition, specifically using a low-viscosity composition with controlled molecular weight oligomers and monomers. This allows the adhesive to flow easily during application, eliminating bubbles, while maintaining optical transparency for improved visibility.
Solution Approach 2:
The patent creates different functional zones within the adhesive composition by combining materials with different properties: oligomers provide structural integrity and transparency, while monomers ensure easy flow and bubble removal during application. This local differentiation of material properties resolves the contradiction between applicability and visibility.
2Illumination intensity
If a transparent acrylic cured product is used to fill the air layer, then visibility is improved, but cure shrinkage is high causing deformation
Solution Approach 1:
The patent employs a composite adhesive system combining oligomers (for low shrinkage and structural stability) with monomers (for ease of curing). This composite approach minimizes overall cure shrinkage while maintaining dimensional stability and optical transparency, resolving the contradiction between visibility and dimensional stability.
Solution Approach 2:
The patent carefully controls the molecular weight and functional group content of the oligomers and monomers to optimize the curing shrinkage parameter. By selecting specific molecular weight ranges and functional group ratios, the adhesive achieves minimal shrinkage during curing while maintaining excellent dimensional stability and optical properties.
3Strength
If adhesive film or adhesive sheet is used, then bonding is achieved, but it is difficult to remove bubbles during adhesion
Solution Approach 1:
The patent uses a liquid adhesive composition that can flow under pressure to displace air bubbles during the bonding process. The low viscosity allows the liquid adhesive to hydrodynamically push out bubbles as it spreads, achieving strong adhesion while eliminating bubbles, unlike rigid adhesive films or sheets.
4Strength
If liquid bonding composition is used for photo-curing, then adhesion is improved, but viscosity control is challenging
Solution Approach 1:
The patent precisely controls the viscosity parameter by selecting oligomers with specific molecular weights (5,000-50,000 g/mol) and monomers with controlled functional group content. This parameter control ensures the liquid adhesive has optimal flow properties for easy application and bubble removal, while maintaining strong adhesion after photo-curing, without requiring complex viscosity control mechanisms.
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 achieves reduced cure shrinkage, improved dimensional stability, and enhanced adhesive properties, preventing deformation and maintaining optical quality over time.
Implementation Method 1
a bonding method of photo-curing a liquid bonding composition in a state where the liquid bonding composition is filled between the image display unit and the protective unit has been used
Data Source
AI summary
Provided is an adhesive composition for optical use, the adhesive composition including: a monofunctional urethane (meth)acrylate-based oligomer; and a polyfunctional urethane (meth)acrylate-based oligomer, in which a weight ratio of the monofunctional urethane (meth)acrylate-based oligomer and the polyfunctional urethane (meth)acrylate-based oligomer is 1:2 to 1:4.