Acrylic Adhesive Sheet for Bubble-Free Display Edge Bonding
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Solution Overview
Problem
Existing adhesive sheets for image display devices face challenges in bonding without air bubbles at the peripheral edge, especially with curved or bent members, and require a balance between flexibility and hardness to prevent crushing and overflow, which is crucial for narrow or frameless designs.
Innovation Solution
An adhesive sheet with an acrylic adhesive layer composed of specific monomers and a stress relaxation rate of 0.20 or less, combined with active energy ray curability, ensuring bonding reliability and resistance to air bubbles and adhesive overflow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the adhesive sheet is made harder to prevent crushing and overflow, then bonding reliability improves, but air bubbles are more likely to be generated at the peripheral edge
Solution Approach 1:
The patent applies parameter changes by precisely controlling the stress relaxation rate (X0) to be 0.20 or less, and the initial modulus of elasticity (G0'(0)) to be within 5 to 100 kPa. These parameter optimizations enable the adhesive sheet to achieve both sufficient hardness for bonding reliability and appropriate flexibility to prevent air bubble generation at the peripheral edge, resolving the technical contradiction between these two opposing requirements.
2Object-generated harmful factors
If the adhesive sheet is made softer to prevent air bubbles at the peripheral edge, then air bubble generation is reduced, but bonding reliability deteriorates
Solution Approach 1:
The patent resolves this contradiction by establishing specific parameter ranges: stress relaxation rate (X0) of 0.20 or less and initial modulus of elasticity (G0'(0)) between 5 to 100 kPa. These optimized parameters enable the adhesive sheet to maintain sufficient softness to prevent air bubble generation while ensuring adequate bonding reliability, achieving a balance that neither extreme alone could provide.
3Area of moving object
If the frame is narrowed to enlarge the effective display region, then display area increases, but bonding at the peripheral edge becomes more difficult
Solution Approach 1:
The patent enables narrow frame designs by optimizing the adhesive sheet parameters: stress relaxation rate (X0) of 0.20 or less and initial modulus of elasticity (G0'(0)) of 5 to 100 kPa. These parameter improvements allow reliable bonding at the peripheral edge even when the frame is narrowed, thus enabling enlargement of the effective display region without sacrificing bonding quality.
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 sheet effectively bonds without air bubbles to the peripheral edge, maintaining flexibility and hardness, suitable for narrow or frameless image display device designs, with improved durability and resistance to deformation.
Implementation Method 1
a stress relaxation rate (X0) is 0.20 or less, wherein the stress relaxation rate (X0) is calculated by the following equation (I) from an initial modulus of elasticity (G0′(0)) at 0.1 seconds after application of a strain of 25% to the acrylic adhesive layer at a temperature of 70° C. and a relaxation modulus of elasticity (G0′(300)) at 300 seconds after application of a strain of 25%
Implementation Method 2
the adhesive sheet with an acrylic adhesive layer composed of specific monomers and a stress relaxation rate of 0.20 or less, combined with active energy ray curability
Data Source
AI summary
The present disclosure provides an adhesive sheet including an acrylic adhesive layer formed of an adhesive composition comprising an acrylic polymer (A), wherein a stress relaxation rate (X0) is 0.20 or less, where the stress relaxation rate (X0) is calculated by the following equation (I) from an initial modulus of elasticity (G0′(0)) at 0.1 seconds after application of a strain of 25% to the acrylic adhesive layer at a temperature of 70° C. and a relaxation modulus of elasticity (G0′(300)) at 300 seconds after application of a strain of 25% to the acrylic adhesive layer at a temperature of 70° C.:Stress relaxation rate (X0)=(G0′(300)/G0′(0)) (I).