Transparent Adhesive Sheet for Optical Members
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing transparent pressure-sensitive adhesive sheets fail to achieve both excellent reworkability and high adhesion when bonding optical members, often resulting in deformation of the display panel, air bubbles, or insufficient removability.
Innovation Solution
A transparent pressure-sensitive adhesive sheet composed of a resin composition with a specific alkoxysilyl group-containing modified hydrogenated block copolymer, a tackifier, and a hydrocarbon-based polymer, which provides a storage modulus within a specific range, enabling excellent adhesion and reworkability by adjusting tackiness and flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a transparent photocurable resin or thermosetting resin is used to fill the gap, then adhesion to the adherend increases, but reworkability cannot be obtained and the display panel may be deformed due to cure shrinkage
Solution Approach 1:
The patent changes the fundamental parameter of the adhesive material from curable resin to pressure-sensitive adhesive, which does not undergo chemical curing. This eliminates cure shrinkage and deformation while maintaining adhesion through controlled tackiness. The pressure-sensitive adhesive is applied in a molten state that fills gaps without shrinking upon setting.
Solution Approach 2:
The patent employs a pressure-sensitive adhesive that can be easily removed and replaced, treating the adhesive as a temporary bonding agent that facilitates assembly and disassembly. This enables reworkability by allowing the adhesive to be peeled off without damaging components, unlike permanent curable resins.
2Ease of operation
If a transparent pressure-sensitive adhesive sheet is used to fill the gap, then the deformation of the display panel is prevented and reworkability is ensured, but both easy reworkability and high tackiness cannot be achieved in a satisfactory manner
Solution Approach 1:
The patent optimizes the molecular weight and composition of the polymer to achieve a specific balance between tackiness and reworkability. By controlling the polymer structure and adding specific additives, the adhesive exhibits high initial tack for strong bonding but maintains enough flexibility and lower glass transition temperature to allow easy removal when needed.
Solution Approach 2:
The patent creates a composite adhesive system combining polymer base resin, plasticizers, and specific additives. This composite formulation achieves both high tackiness through optimized composition and easy reworkability through controlled material properties, resolving the contradiction between strong bonding and easy removal.
3Illumination intensity
If the gap is filled with a transparent filling material, then visibility is improved, but air bubbles may be easily mixed when filling the gap with curable resin
Solution Approach 1:
The patent replaces the chemical curing process with a physical bonding mechanism. The pressure-sensitive adhesive bonds through pressure and adhesion without chemical reaction, eliminating the need for curing steps where air bubbles could be trapped. The adhesive is applied in molten state and sets by cooling, allowing air bubbles to escape naturally.
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 exhibits excellent reworkability at low temperatures and strong adhesion at high temperatures, ensuring effective bonding and recyclability of optical members without deformation or air bubbles, while maintaining transparency and mechanical strength.
Implementation Method 1
a specific alkoxysilyl group-containing modified hydrogenated block copolymer
Implementation Method 2
has a storage modulus at 25°C within a specific range
Data Source
AI summary
The present invention is a transparent pressure-sensitive adhesive sheet that is formed of a resin composition [F], and has a storage modulus at 25°C of 1×106 to 1×108 Pa, the resin composition [F] comprising a modified hydrogenated block copolymer [E] as a main component, the modified hydrogenated block copolymer [E] being obtained by introducing an alkoxysilyl group into a hydrogenated block copolymer [D], the hydrogenated block copolymer [D] being obtained by hydrogenating 90% or more of unsaturated bonds of a block copolymer [C] that comprises at least two polymer blocks [A] comprising a specific compound and at least one polymer block [B] comprising a specific compound, and a ratio (wA:wB) of a total weight fraction wA of the polymer block [A] in the block copolymer [C] to a total weight fraction wB of the polymer block [B] in the block copolymer [C] being 20:80 to 60:40.