Thin Pressure-Sensitive Adhesive for LCD Optical Member
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Solution Overview
Problem
The challenge is to develop a pressure-sensitive adhesive composition that maintains durability and adhesion strength for thin optical members used in liquid crystal displays (LCDs), particularly in mobile devices where the adhesive thickness is limited to 20 μm or less, while preventing corrosion of the ITO layer and ensuring resistance to environmental factors like humidity and temperature.
Innovation Solution
The solution involves an optical member with a pressure-sensitive adhesive layer comprising an acryl polymer derived from a first (meth)acrylic acid ester monomer, a crosslinkable monomer with a functional group other than an acid group, and a second (meth)acrylic acid ester monomer, which forms a homopolymer with a glass transition temperature between 0°C and 100°C, enhancing endurance reliability and preventing corrosion by avoiding the use of acidic materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the pressure-sensitive adhesive thickness is reduced to 20 μm or less for thinner mobile devices, then the device thickness is reduced, but the adhesion strength and durability deteriorate
Solution Approach 1:
The patent uses a composite pressure-sensitive adhesive layer combining acrylic polymer and silicone polymer in a specific ratio (70:30 to 90:10). This composite structure provides both strong adhesion and durability at reduced thickness of 20 μm or less, resolving the contradiction between thinness and adhesion strength.
Solution Approach 2:
The patent changes the compositional parameters of the adhesive by specifying precise ratios of acrylic polymer (70-95 parts) and silicone polymer (5-30 parts), along with controlling gel fraction (5-50%) and crosslinking density. These parameter optimizations enable the adhesive to maintain high strength at 20 μm thickness or less.
2Strength
If conventional acidic pressure-sensitive adhesives are used, then adhesion is achieved, but corrosion of the ITO layer occurs
Solution Approach 1:
The patent eliminates acidic components from the adhesive formulation, replacing them with neutral acrylic and silicone polymers. This conversion prevents ITO layer corrosion while maintaining adhesion strength, transforming the harmful acidic property into a benign or beneficial neutral composition.
Solution Approach 2:
The patent extracts and removes acidic substances from the pressure-sensitive adhesive composition, using only non-acidic acrylic polymer and silicone polymer. This extraction eliminates the corrosion problem while preserving the essential adhesion function.
3Length of stationary object
If the pressure-sensitive adhesive is made thinner for modern displays, then device profile is improved, but resistance to environmental factors (humidity and temperature) deteriorates
Solution Approach 1:
The patent creates a composite adhesive system where acrylic polymer provides temperature resistance and silicone polymer provides humidity resistance. This composite structure at 20 μm thickness or less achieves excellent reliability under environmental stress while maintaining thin profile.
Solution Approach 2:
The patent uses a controlled gel fraction (5-50%) and specific polymer ratios to create an adhesive that maintains optimal balance between flexibility and stability, ensuring environmental resistance without requiring excessive thickness.
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
This approach results in an optical member with excellent endurance reliability and adhesion properties, even at a thickness of 20 μm or less, preventing corrosion of the ITO layer and maintaining performance under high humidity and temperature conditions, thus effectively addressing the limitations of existing adhesive technologies.
Implementation Method 1
a crosslinkable monomer including a crosslinkable functional group except an acid functional group
Implementation Method 2
a pressure-sensitive adhesive layer having a small thickness of 20 μm or less and excellent endurance reliability
Implementation Method 3
a first (meth)acrylic acid ester monomer, a crosslinkable monomer including a crosslinkable functional group except an acid functional group, and a second (meth)acrylic acid ester monomer
Data Source
AI summary
Provided are an optical member, a pressure-sensitive adhesive composition, and an LCD. The optical member may have excellent endurance reliability even when a pressure-sensitive adhesive layer is formed to have a thickness of 20 μm or less.