Heat-Cured Polarizing Plate Barrier Layer for Moisture Resistance
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Solution Overview
Problem
Existing polarizing plates with a protective film only on one side are vulnerable to external moisture and suffer from decolorization under high temperature/humidity conditions, and the use of UV curable compositions complicates the manufacturing process and limits the improvement of light transmittance and polarization.
Innovation Solution
A polarizing plate with a barrier layer formed through heat curing, comprising a (meth)acrylic copolymer, a polyisocyanate curing agent with alkylene groups and an isocyanurate group-containing polyisocyanate curing agent, and a silane coupling agent, which provides good moisture blocking and adhesion to the polarizer without an additional adhesive layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a protective film is formed only on the light exit surface of the polarizer, then the thickness of the polarizing plate is reduced, but the polarizing plate becomes more vulnerable to external moisture
Solution Approach 1:
The invention divides the protective function into two separate layers: a protective film on the light exit surface and a barrier layer on the light incident surface. This segmentation allows each layer to perform its specific function optimally while maintaining overall thinness of the polarizing plate.
Solution Approach 2:
The invention applies different material properties to different surfaces: the protective film on the light exit surface provides mechanical protection, while the barrier layer on the light incident surface provides moisture blocking. This local differentiation of material quality addresses the specific needs of each surface.
2Ease of manufacture
If a UV curable composition is used for the barrier layer, then ease of manufacture is improved, but an additional adhesive layer is required which complicates the manufacturing process
Solution Approach 1:
The invention merges the barrier layer function and adhesive layer function into a single heat-curable composition. This composition provides both moisture blocking and adhesion to the polarizer, eliminating the need for a separate adhesive layer and simplifying the manufacturing process.
Solution Approach 2:
The heat-curable composition serves multiple functions simultaneously: it acts as a barrier layer to block moisture, an adhesive layer to attach to the polarizer, and provides structural support. This multi-functionality reduces the number of separate components needed.
3Reliability
If a typical barrier layer is formed to reduce variation in light transmittance and suppress crack generation, then adhesion to polarizer is improved, but the ability to prevent dye decolorizing is limited
Solution Approach 1:
The invention uses a composite material system consisting of a (meth)acrylic copolymer as the base resin and a polyisocyanate compound as the curing agent. This composite provides both strong adhesion to the polarizer and effective prevention of dye decolorizing under high temperature and humidity conditions.
Solution Approach 2:
The invention changes the chemical composition parameters of the barrier layer by selecting specific (meth)acrylic copolymers with appropriate glass transition temperatures and molecular weights, combined with polyisocyanate compounds. These parameter changes enable the barrier layer to resist dye decolorizing while maintaining adhesion.
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 heat-cured barrier layer effectively blocks external moisture, minimizes polarizer decolorization, and simplifies the manufacturing process by eliminating the need for an adhesive layer, while maintaining good adhesion to the polarizer.
Implementation Method 1
a silane coupling agent
Implementation Method 2
a curing agent including a mixture of a polyisocyanate curing agent having a plurality of units, each containing an alkylene group having a urethane bond and at least two carbon atoms, and an isocyanurate group-containing polyisocyanate curing agent
Data Source
AI summary
Provided are a polarizing plate and an optical display device comprising same, wherein: the polarizing plate comprises a polarizer, a protection film formed on the surface of the polarizer, and a barrier layer formed on the other surface of the polarizer; the barrier layer is formed of a composition comprising a (meth)acryl-based copolymer, a curing agent, and a silane coupler; and the curing agent comprises a mixture of: a polyisocyanate curing agent containing a plurality of units, each containing an entirety of an alkylene group of two or more carbon atoms having a urethane bonding; and a polyisocyanate curing agent containing an isocyanurate group.