Transparent Adhesive Sheet for Optical Bonding
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Solution Overview
Problem
Existing transparent pressure-sensitive adhesive sheets used for bonding optical members in liquid crystal display devices face challenges with achieving excellent optical properties, adhesion, and reworkability, particularly due to issues with birefringence and mechanical strength when produced using melt extrusion methods.
Innovation Solution
A transparent pressure-sensitive adhesive sheet is developed with a hydrogenated triblock copolymer film and acrylic-based pressure-sensitive adhesive layers, where the hydrogenated triblock copolymer is formed by hydrogenating 90% or more of the unsaturated bonds of a block copolymer with a specific ratio of aromatic vinyl and linear conjugated diene units, and the adhesive layers are applied on both sides of the film to enhance optical properties and reworkability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the content of repeating units derived from aromatic vinyl compounds is increased to form a film with small retardation using melt extrusion, then optical properties (transparency and low birefringence) are improved, but the film becomes hard and fragile with decreased mechanical strength
Solution Approach 1:
The patent applies parameter changes by controlling the composition ratio of polymer blocks (aromatic vinyl compound units at 30-70 wt%, linear conjugated diene compound units at 30-70 wt%) and adjusting molecular weight parameters to achieve the optimal balance between low retardation and adequate mechanical strength in the extruded film
Solution Approach 2:
The patent uses composite materials by creating a block copolymer structure that combines aromatic vinyl compound polymer blocks (for low birefringence) with linear conjugated diene compound polymer blocks (for mechanical strength and flexibility), achieving synergistic effects that resolve the contradiction between optical properties and mechanical strength
2Strength
If a transparent pressure-sensitive adhesive sheet is designed for excellent adhesion, then bonding strength is improved, but reworkability (ease of removal and recycling) deteriorates
Solution Approach 1:
The patent applies segmentation by dividing the adhesive sheet into distinct functional layers: a pressure-sensitive adhesive layer (providing adhesion) and a base film layer made of hydrogenated block copolymer (providing reworkability and optical properties). This layered structure allows each layer to perform its specific function independently
Solution Approach 2:
The patent applies local quality by giving different properties to different parts of the adhesive sheet: the adhesive layer has high bonding strength for secure attachment, while the base film has specific mechanical properties (controlled by block copolymer composition) that enable easy removal and recycling, with each layer optimized for its local function
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 provides a transparent pressure-sensitive adhesive sheet with excellent transparency, low birefringence, strong adhesion, and reworkability, suitable for optical applications, such as bonding touch panels and display devices, while maintaining mechanical strength and reducing the risk of breakage during removal.
Implementation Method 1
a transparent pressure-sensitive adhesive sheet comprises a film that is formed of a hydrogenated triblock copolymer, and a layer that is formed of a transparent pressure-sensitive adhesive, the layer being formed on each side of the film, the hydrogenated triblock copolymer being obtained by hydrogenating 90% or more of the unsaturated bonds of a block copolymer
Data Source
AI summary
The present invention is a transparent pressure-sensitive adhesive sheet comprising a film that is formed of a hydrogenated block copolymer [D], and a layer that is formed of a transparent pressure-sensitive adhesive [E], the layer being formed on each side of the film, 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] and at least one polymer block [B], the polymer block [A] comprising a repeating unit derived from an aromatic vinyl compound, the polymer block [B] comprising a repeating unit derived from a linear conjugated diene compound. The present invention provides a transparent pressure-sensitive adhesive sheet (double-sided, transparent pressure-sensitive adhesive sheet) that is used to bond two optical members (adherends), and exhibits excellent optical properties (transparency and low birefringence), adhesion, and reworkability