Polarizing Plate With Epoxy Bonding to Block Iodine Elution
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Solution Overview
Problem
Light emitting diode displays, such as OLEDs, suffer from visibility and contrast issues due to external light reflection and iodine elution from polarizers under high temperature/humidity conditions, leading to deterioration and color change of the retardation layer.
Innovation Solution
A polarizing plate with a first bonding layer and a first retardation layer, composed of a cured non-(meth)acrylic composition containing a mixture of bifunctional epoxy compounds and a photoinitiator, including an iodonium-based photo-acid generator and an anthracene-based photosensitizer, to enhance peel strength and prevent iodine penetration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a liquid crystal retardation layer is used to reduce thickness, then the polarizing plate becomes thinner, but iodine elution from the polarizer causes color change and corrosion under high temperature/humidity conditions
Solution Approach 1:
An iodine-blocking layer is introduced as an intermediary component between the polarizer and the liquid crystal retardation layer. This layer specifically blocks iodine elution from the polarizer, preventing color change and corrosion of the retardation layer while maintaining the thin-profile benefits of the liquid crystal structure.
Solution Approach 2:
The polarizing plate employs a composite structure combining multiple materials: polarizer, iodine-blocking layer, liquid crystal retardation layer, and bonding layers. This composite approach allows each layer to perform its specific function, with the iodine-blocking layer providing chemical protection while the liquid crystal layer provides optical functionality with minimal thickness.
2Illumination intensity
If the liquid crystal retardation layer has high light transmittance in UVA range, then UV protection is improved, but peel strength between layers decreases
Solution Approach 1:
The bonding layer uses a non-(meth)acrylic composition with specific epoxy compounds and photoinitiators that cure to provide high peel strength. The composition parameters are optimized to achieve both strong adhesion (peel strength of 50 N/15 mm or more) and appropriate UV transmittance, resolving the contradiction between bonding strength and light transmission.
3Reliability
If a polarizing plate is provided to prevent external light reflection, then visibility and contrast are improved, but iodine elution from the polarizer causes deterioration of the retardation layer under high temperature/humidity conditions
Solution Approach 1:
The iodine-blocking layer serves as a protective intermediary that intercepts iodine molecules eluting from the polarizer, preventing them from reaching and deteriorating the liquid crystal retardation layer. This allows the polarizing plate to maintain its antireflection functionality while protecting against chemical degradation.
Solution Approach 2:
The iodine-blocking layer converts the harmful iodine elution into a contained phenomenon, where iodine is blocked and prevented from causing damage. The layer essentially transforms a potential failure mode into a controlled, non-damaging process by providing a sacrificial barrier.
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 solution effectively prevents iodine elution and maintains high peel strength between the polarizer and retardation layer, improving visibility and reducing reflection even under high temperature/humidity conditions.
Implementation Method 1
the photoinitiator includes a mixture of an iodonium-based photo-acid generator and an anthracene-based photosensitizer
Implementation Method 2
the photoinitiator includes a mixture of an iodonium-based photo-acid generator and an anthracene-based photosensitizer
Implementation Method 3
the first retardation layer has a light transmittance of 1.0% or less in the UVA wavelength range
Implementation Method 4
sufficiently or suitably prevents or reduces penetration of iodine eluted from a polarizer into a retardation layer
Data Source
AI summary
A polarizing plate and an optical display apparatus are disclosed. The polarizing plate includes: a polarizer; and a first bonding layer and a first retardation layer sequentially stacked on a lower surface of the polarizer. The first retardation layer has a light transmittance of 1.0% or less in the UVA wavelength range. The first bonding layer includes a cured product of a non-(meth)acrylic composition including a curable compound and a photoinitiator, and the curable compound includes an epoxy compound, the epoxy compound including a mixture of a bifunctional alicyclic epoxy compound, a bifunctional aromatic epoxy compound, and a bifunctional aliphatic epoxy compound. The photoinitiator includes a mixture of an iodonium-based photo-acid generator and an anthracene-based photosensitizer, the anthracene-based photosensitizer being present in an amount of 0.5 parts by weight or more relative to 100 parts by weight of the curable compound.