Optical Transparent Adhesive Sheet for Display Devices
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Optically clear adhesive sheets used in touchscreen display devices face challenges such as air gaps causing interfacial reflection, low adhesive strength, corrosion of metal components, and issues with moisture resistance, especially in high-humidity environments, which affect the visibility and durability of the display panel.
Innovation Solution
A thermosetting polyurethane composition is developed using an olefin-based polyol component and a polyisocyanate component with a polyethylene oxide unit, which reduces moisture absorption and haze, maintaining transparency and flexibility even in high-humidity conditions, and is suitable for bonding display panels and touchscreens with uneven surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a general-purpose adhesive is used to bond the transparent resin sheet and transparent substrate, then the bonding process is simple, but the adhesive dries and forms a visible line that deteriorates appearance and may cause display abnormalities
Solution Approach 1:
The patent extracts the adhesive function from a separate general-purpose adhesive layer and integrates it into the transparent resin sheet itself through a silane-modified oligomer component that provides inherent adhesive properties. This eliminates the need for a separate adhesive layer and the associated drying line problems while maintaining bonding capability.
Solution Approach 2:
The transparent resin sheet uses a composite material system combining a base resin with silane-modified oligomers that provide both structural transparency and adhesive functionality. This composite approach allows the single layer to perform both optical and bonding functions without creating visible bond lines.
2Manufacturing precision
If a transparent resin sheet with adhesive properties is used, then bond line visibility is eliminated, but the adhesive strength may be insufficient for reliable bonding
Solution Approach 1:
The patent modifies the chemical parameters of the resin system by incorporating silane-modified oligomers with specific functional groups that enhance adhesive strength through chemical bonding mechanisms. The silane groups can form crosslinked structures that significantly improve bond strength while maintaining transparency.
Solution Approach 2:
The transparent resin sheet employs a composite material system where silane-modified oligomers are combined with base resins to create a material that simultaneously achieves optical clarity and high adhesive strength through synergistic material properties and crosslinking chemistry.
3Strength
If the silane-modified oligomer content is increased to improve adhesive strength, then bonding improves, but the resin may prematurely crosslink during storage or processing
Solution Approach 1:
The silane modification is performed in advance on the oligomers before they are incorporated into the resin sheet, creating pre-modified oligomers that are stable during storage but become reactive under specific processing conditions. This preliminary modification allows the system to maintain stability until activation.
Solution Approach 2:
The patent incorporates hydrophilic groups and specific molecular structures that act as cushioning elements to prevent premature crosslinking by controlling the reactivity timing. These structural features stabilize the oligomers during storage while enabling crosslinking only when intended through moisture exposure or heat treatment.
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 effectively reduces whitening and maintains high transparency in high-humidity environments while providing excellent flexibility and adhesive strength, ensuring the optical clarity and durability of the display device.
Implementation Method 1
it has gradually come to light by experimentation that a crosslinked structure formed by silane crosslinking has high peeling strength
Implementation Method 2
it has gradually come to light by experimentation that adhesion is generated by a hydrophilic group absorbing moisture from the atmosphere
Implementation Method 3
a transparent resin sheet having a specific structure and specific adhesive properties is used to bond a transparent substrate and a polarizing plate
Data Source
Figure 1~2
Figure 3~4(b)
AI summary
The present invention provides an optically clear adhesive sheet with excellent environment resistance using a thermosetting polyurethane composition that has excellent flexibility and is capable of giving a thick film. The optically clear adhesive sheet of the present invention contains: a cured product of a thermosetting polyurethane composition, the thermosetting polyurethane composition containing an olefin-based polyol component and a polyisocyanate component, the optically clear adhesive sheet exhibiting a moisture absorption of 1.0 wt% or lower after being subjected to a test in a high-temperature, high-humidity environment for eight hours and exhibiting a haze of 1.5% or lower after being subjected to the test in a high-temperature, high-humidity environment for 100 hours, wherein the test in a high-temperature, high-humidity environment is performed at a temperature of 85°C and a humidity of 85%.