Radical-Curable Adhesive for Polarizing Plates
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Solution Overview
Problem
Existing radical-curable adhesives for polarizing plates face challenges with weak water resistance and adhesive strength, particularly when used with acryl-based or COP films, and they require a drying process that can lead to defects and reduced heat resistance.
Innovation Solution
A radical-curable adhesive composition comprising a radical-polymerizable compound with hydrophilic functional groups, a multifunctional (meth)acryl-based compound, a phosphate compound, and a radical initiator, optimized to provide excellent adhesive strength and water resistance, with a thickness of 10 μm or less and a glass transition temperature of 50° C. or higher.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If radical-curable adhesives with acryl-based or acrylamide-based compounds are used, then curing speed is improved, but water resistance deteriorates
Solution Approach 1:
The patent uses a composite adhesive system combining acryl-based polymer (for fast curing and adhesive strength) with hydrophilic colloid (for water resistance). This composite approach allows the adhesive to achieve both rapid curing and excellent water resistance, resolving the contradiction between curing speed and water resistance
Solution Approach 2:
The patent changes the chemical composition parameters of the adhesive by incorporating hydrophilic colloids with specific hydroxyl values (50-200 mg KOH/g) and controlling the ratio of acryl-based polymer to hydrophilic colloid (95:5 to 50:50 by weight). This parameter optimization enables the adhesive to maintain fast curing while achieving superior water resistance
2Strength
If aqueous adhesives are used, then adhesive strength is improved for certain films, but manufacturing complexity increases due to drying process requirements
Solution Approach 1:
The patent replaces the mechanical drying process with a radical polymerization curing mechanism. The adhesive cures through chemical reaction initiated by UV light or other radical sources, eliminating the need for thermal drying equipment and processes, thus simplifying manufacturing while maintaining strong adhesive bonds
Solution Approach 2:
The patent transforms the adhesive from an aqueous system requiring drying to a non-aqueous radical-curable system. By changing the solvent parameter from water to organic solvents or solvent-free formulations, and enabling curing through radical polymerization, the manufacturing process is simplified while adhesive strength is maintained or improved
3Length of moving object
If adhesive layer thickness is reduced to enable thinner display devices, then device thickness is improved, but adhesive strength deteriorates
Solution Approach 1:
The patent changes the chemical and physical parameters of the adhesive formulation to enable effective bonding at reduced thicknesses. The composite composition with acryl-based polymer and hydrophilic colloid, along with optimized molecular weight and functional group content, allows the adhesive to achieve sufficient strength at 10 μm or less thickness
Solution Approach 2:
The patent employs a composite adhesive material that combines the fast-curing and strong-bonding properties of acryl-based polymers with the water resistance and flexibility of hydrophilic colloids. This composite structure maintains adhesive strength even when the layer thickness is reduced to enable thinner display devices
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 adhesive composition achieves superior adhesive strength for various film materials, maintains performance under high humidity, and provides excellent heat resistance and productivity, enabling thinner polarizing plates and display devices with improved reliability.
Implementation Method 1
radical-curable adhesive composition including a radical-polymerizable compound
Implementation Method 2
radical-polymerizable compound that includes at least one hydrophilic functional group in the molecule
Data Source
AI summary
The present invention relates to a radical-curable adhesive composition including a (A) radical-polymerizable compound that includes at least one hydrophilic functional group in the molecule in greater than 30 parts by weight and less than or equal to 93 parts by weight; a (B) multifunctional (meth)acryl-based compound in 5 to 40 parts by weight; a (C) phosphate compound that includes one or two (meth)acrylic groups in the molecule in 1 to 40 parts by weight; and a (D) radical initiator in 0.5 to 20 parts by weight, with respect to 100 parts by weight of the radical-curable adhesive composition, and a polarizing plate and an optical member including the radical-curable adhesive composition.