Adhesive Composition for Polarizing Plates Shrinkage Control
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Solution Overview
Problem
Polarizing plates using aqueous adhesives suffer from dimensional changes due to heat, leading to light leakage and inconsistent curing, while cation polymerizable UV curing adhesives are prone to moisture-induced issues and shrinkage, necessitating strict control of environmental conditions.
Innovation Solution
An adhesive composition comprising a (meth)acrylic radical compound, a cationic epoxy compound, a phenoxy resin, and a photoinitiator, which provides strong adhesion, high reliability, and improved wet-heat resistance, with the (meth)acrylic radical compound enhancing interface adhesion and the cationic epoxy compound providing cohesion, while the phenoxy resin improves physical cohesion and cross-linking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If cation polymerizable UV curing adhesive is used to avoid dimensional change, then adhesion strength is improved, but the adhesive becomes vulnerable to moisture and requires strict control of surrounding moisture and PVA-based polarizer moisture content
Solution Approach 1:
The patent uses a composite adhesive system combining cation polymerizable compounds (for strong adhesion) with silane-modified compounds (for moisture resistance). This composite approach allows the adhesive to maintain high bonding strength while inherently resisting moisture interference, eliminating the need for strict moisture control during curing.
Solution Approach 2:
The patent modifies the chemical parameters of the adhesive by introducing silane-modified cation polymerizable compounds. This parameter change transforms the adhesive's properties to achieve both high adhesion strength and moisture resistance simultaneously, resolving the contradiction between strength and moisture sensitivity.
2Strength
If cation polymerizable UV curing adhesive is used, then adhesion is improved, but the cured product is easily wound during storage when prepared in wound roll form
Solution Approach 1:
The patent incorporates silane-modified cation polymerizable compounds that undergo preliminary stabilization. These compounds are designed to remain stable during storage and only activate under controlled UV irradiation conditions, preventing premature curing and winding issues while maintaining strong adhesion when properly cured.
Solution Approach 2:
The silane-modified compounds act as intermediaries between the cation polymerizable compounds and the final cured structure. They provide a stable intermediate state during storage that prevents winding, while still enabling strong adhesion formation when activated by UV light.
3Ease of operation
If aqueous adhesive is used, then ease of application is maintained, but dimensional change occurs due to heat from backlight causing screen distortion and light leakage
Solution Approach 1:
The patent changes the physical parameters of the adhesive by using silane-modified cation polymerizable compounds instead of aqueous formulations. This parameter change eliminates water content that causes dimensional instability under heat, while maintaining ease of application through UV-curable liquid state before curing.
Solution Approach 2:
The patent replaces the water-based evaporation mechanism of aqueous adhesives with a UV-photochemical curing mechanism. This substitution eliminates the dimensional changes associated with water evaporation and heat exposure, while maintaining application ease through the liquid state before curing.
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 a maximum shrinkage length of 2 mm or less in polarizing plates when exposed to warm water, ensuring consistent curing and maintaining adhesion, reliability, and water resistance, while maintaining a suitable viscosity for coatability.
Implementation Method 1
a cation polymerizable UV curing adhesive is proposed instead of the aqueous adhesives
Implementation Method 2
the polarizer has a maximum shrinkage length of about 2 mm or less at one end thereof when the polarizing plate is dipped in water having constant temperature of 60° C. for 2 hours
Data Source
AI summary
Disclosed are an adhesive composition for polarizing plates, a polarizing plate using the same, a method for preparing the same, and an optical member including the same. The adhesive composition includes (A) a (meth)acrylic radical compound, (B) a cationic epoxy compound, (C) a phenoxy resin, and (D) a photoinitiator.