Adhesive Layer for Polarizing Plate Microbubble Prevention
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Solution Overview
Problem
Polarizing plates face issues with microbubble generation and durability when exposed to high temperatures due to volatile organic compounds escaping through protective films with varying water vapor transmission rates, leading to undesirable appearances and reduced durability.
Innovation Solution
An adhesive layer with a storage modulus of 8×10^3 Pa or more at 85°C, composed of a (meth)acrylic copolymer with a weight average molecular weight of 800,000 g/mol, a curing agent, and a silane coupling agent, is used to adhere protective films with a water vapor transmission rate of 100 g/m²/day or less, preventing microbubble formation and ensuring durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If protective films with low water vapor transmission rate are used, then cost and optical properties are improved, but microbubble generation occurs due to volatile organic compounds trapped inside
Solution Approach 1:
A bubble inhibitor is introduced as an intermediary substance within the adhesive layer to prevent microbubble formation. The bubble inhibitor specifically targets and suppresses the generation of microbubbles caused by volatile organic compounds trapped between the protective film and adhesive, resolving the contradiction between using low-WVTR protective films and preventing microbubble defects
Solution Approach 2:
The adhesive is formulated as a composite material system comprising a (meth)acrylic copolymer with specific molecular weight (800,000 g/mol or more), curing agents, and bubble inhibitors. This composite formulation provides both strong adhesion to low-WVTR protective films and effective suppression of microbubble generation through the synergistic action of its components
2Reliability
If adhesive storage modulus is increased to prevent microbubbles, then durability is improved, but adhesive flexibility may be reduced
Solution Approach 1:
The adhesive formulation parameters are precisely controlled: the (meth)acrylic copolymer has a weight average molecular weight of 800,000 g/mol or more, and the storage modulus at 85°C is maintained within the range of 8×10³ Pa or more. These parameter specifications ensure the adhesive achieves sufficient stiffness to prevent microbubble formation while retaining adequate flexibility for proper bonding
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 layer effectively prevents microbubble generation and maintains excellent durability of polarizing plates even at high temperatures, ensuring consistent performance and appearance.
Implementation Method 1
a silane coupling agent
Implementation Method 2
a curing agent; wherein an adhesive layer prepared from the adhesive has a storage modulus, after curing
Data Source
AI summary
An adhesive for adhering a protective film, the protective film having a water vapor transmission rate of about 100 g/m2·day or less at 40° C. and about 90% RH during manufacture of an optical member including a polarizing plate, a polarizing plate including an adhesive layer prepared from the adhesive, and an optical member including the polarizing plate, the adhesive including a (meth)acrylic copolymer, the (meth)acrylic copolymer having a weight average molecular weight of about 800,000 g/mol or more; a curing agent; and a silane coupling agent, wherein an adhesive layer prepared from the adhesive has a storage modulus, after curing, of about 8×103 Pa or more at about 85° C. and a frequency of about 10−3 rad/s to about 102 rad/s.