Acrylic Adhesive Sheet Balancing Edge Bubble Suppression and Overflow
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Solution Overview
Problem
Existing adhesive sheets for image display devices face challenges in bonding without air bubbles near the peripheral edge, especially in designs with narrow or frameless frames, and fail to maintain bonding reliability and prevent adhesive overflow, particularly in curved or bent surfaces.
Innovation Solution
An adhesive sheet with an acrylic adhesive layer composed of specific components, including an acrylic polymer, crosslinking agent, and photoinitiator, achieving a stress relaxation rate of 0.25 or more, initial modulus of elasticity between 5 to 100 kPa, and relaxation modulus of elasticity between 1.3 to 100 kPa, ensuring bonding without air bubbles and reducing adhesive overflow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the adhesive sheet is made harder to prevent adhesive overflow and crushing, then adhesive overflow is reduced, but air bubbles are more likely to be generated in the peripheral edge
Solution Approach 1:
The patent applies parameter changes by precisely controlling the stress relaxation rate (0.25 or more) and modulus of elasticity (5 to 100 kPa) of the acrylic adhesive layer. This allows the adhesive to have optimal balance between hardness and flexibility, preventing both adhesive overflow and air bubble generation. The specific parameter ranges enable the adhesive to maintain suitable hardness while avoiding excessive rigidity that would cause bonding failures at peripheral edges.
2Reliability
If the adhesive sheet is made more flexible to improve bonding at peripheral edges, then bonding reliability improves, but adhesive overflow and crushing increase
Solution Approach 1:
The patent resolves this contradiction by establishing specific parameter ranges for the acrylic adhesive layer: stress relaxation rate of 0.25 or more and modulus of elasticity between 5 to 100 kPa. These parameter changes enable the adhesive to achieve optimal flexibility for bonding at peripheral edges while maintaining sufficient hardness to prevent overflow and crushing, eliminating the need to choose between the two opposing requirements.
3Area of moving object
If the frame is narrowed to enlarge effective display region, then display area increases, but bonding without air bubbles becomes more difficult
Solution Approach 1:
The patent enables narrow frame designs by applying parameter changes to the acrylic adhesive layer, specifically controlling the stress relaxation rate (0.25 or more) and modulus of elasticity (5 to 100 kPa). These parameter adjustments allow the adhesive to maintain high bonding reliability even in the constrained peripheral edge areas of narrow frame designs, ensuring bond strength matches that of the central region and preventing air bubble formation despite the reduced bonding area.
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 provides superior bonding reliability and prevents air bubbles and adhesive overflow, suitable for narrow or frameless designs and curved surfaces, enhancing the appearance and functionality of image display devices.
Implementation Method 1
an acrylic adhesive layer, wherein a stress relaxation rate is 0.25 or more
Implementation Method 2
bonding an adhesive sheet primarily crosslinked by ultraviolet rays to an image display device constituent member, and then irradiating the adhesive sheet with ultraviolet rays through the image display device constituent member to secondarily cure the adhesive sheet
Data Source
AI summary
The present disclosure provides an adhesive sheet including an acrylic adhesive layer.