Transparent Double-Sided Adhesive Sheet for Step Conformity and Cutting
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Solution Overview
Problem
Existing self-adhesive sheets struggle to conform to surface irregularities and steps in image display devices, leading to poor appearance and reliability issues, while maintaining transparency and processability.
Innovation Solution
A transparent double-sided self-adhesive sheet with a multilayer structure, using (meth)acrylic acid ester series copolymers, where the intermediate layer has a higher shear storage elastic modulus than the surface layers, and indentation hardness between 10 to 80, allowing it to conform to surface irregularities and maintain cutting processability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the self-adhesive sheet is made soft to conform to surface irregularities and steps, then the ability to conform to surface irregularities is improved, but the cutting processability deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the viscoelastic properties of the pressure-sensitive adhesive layer. Specifically, it sets the storage elastic modulus G′ at 1 Hz between 5×10³ to 5×10⁵ Pa and at 10⁻⁷ Hz between 5×10¹ to 5×10³ Pa, creating an optimal balance between softness for conforming to surface irregularities and structural integrity for cutting processability
Solution Approach 2:
The patent uses composite materials by formulating the pressure-sensitive adhesive layer with a specific composition including (meth)acrylic acid ester series polymer as the base resin, combined with other additives and modifiers to achieve the desired viscoelastic profile that simultaneously provides conformability and processability
2Ease of manufacture
If the self-adhesive sheet is made hard to maintain cutting processability, then the cutting processability is improved, but the ability to conform to surface irregularities and adhesive strength deteriorates
Solution Approach 1:
The patent resolves this contradiction by implementing specific parameter changes in the viscoelastic profile. The storage elastic modulus is controlled to be higher at 1 Hz (5×10³ to 5×10⁵ Pa) for cutting stability and lower at 10⁻⁷ Hz (5×10¹ to 5×10³ Pa) for conformability, creating a frequency-dependent mechanical response that satisfies both requirements
3Adaptability or versatility
If expanded foam is used to improve the ability to conform to surface irregularities, then the conformability is improved, but the transparency is lost
Solution Approach 1:
The patent avoids using expanded foam by changing the material parameter approach. Instead, it uses a transparent pressure-sensitive adhesive layer with controlled viscoelastic properties that provides conformability through molecular-level adaptation rather than physical expansion, thereby maintaining optical transparency while achieving surface conformability
4Reliability
If the self-adhesive sheet is made soft to achieve close contact with steps and surface irregularities, then the adhesive strength is improved, but the cutting processability and handling deteriorate
Solution Approach 1:
The patent resolves this contradiction through parameter changes in the viscoelastic spectrum. The storage elastic modulus is optimized at different frequencies: higher values at 1 Hz provide structural rigidity for handling and cutting, while lower values at 10⁻⁷ Hz enable molecular adaptation and close contact with surface irregularities for strong adhesion
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 sheet effectively adheres to image display panels without air bubbles, conforming to surface irregularities and ensuring long-term reliability and processability, suitable for bonding protective and touch panels in devices like LCDs and TVs.
Implementation Method 1
the storage elastic modulus G′ (1 Hz) at a measurement temperature of 20° C. and a frequency of 1 Hz is 5×10³ to 5×10⁵ Pa and that the storage elastic modulus G′ (10⁻⁷ Hz) at a standard temperature of 20° C. and a frequency of 10⁻⁷ Hz is 5×10¹ to 5×10³ Pa
Data Source
AI summary
A transparent double-sided self-adhesive sheet is provided which, when bonding to an adherend, not only excels in the ability to conform to steps or surface irregularities caused by a printing site, but also excels in workability such as cutting processability. A transparent double-sided self-adhesive sheet is proposed, having an intermediate resin layer (A) and pressure-sensitive adhesive layers (B) as front and reverse side layers, each of the layers being a layer having one or more species of (meth)acrylic acid ester series (co)polymer as the base resin, in which transparent double-sided self-adhesive sheet, the shear storage elastic modulus (G′(A)) at a frequency of 1 Hz of the intermediate resin layer (A) is higher than the pressure-sensitive adhesive layers (B) in a temperature range of 0° C. to 100° C., and, the indentation hardness (ASKER C2 hardness) of the entire sheet is 10 to 80.