Polymerizable Composition for Wavelength Conversion Layer Oxygen Barrier
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Solution Overview
Problem
The brightness of liquid crystal display devices with wavelength conversion layers containing quantum dots decreases in the outer peripheral regions due to oxygen permeation, leading to image quality deterioration, as the emission efficiency of quantum dots is compromised by photooxidation reactions.
Innovation Solution
A polymerizable composition is developed, comprising quantum dots with ligands having saturated hydrocarbon chains, a polymerizable compound with a LogP value of 3.0 or lower, and a dispersant with both nonpolar and polar portions, which reduces oxygen permeability and improves dispersion stability, thereby forming a wavelength conversion layer with enhanced brightness and reduced brightness unevenness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a barrier layer is laminated on the wavelength conversion layer to protect quantum dots from oxygen, then the emission efficiency is improved, but the device complexity increases
Solution Approach 1:
The invention merges the barrier layer function with the wavelength conversion layer by making the wavelength conversion layer itself oxygen-barrier type. This integration eliminates the need for a separate barrier layer while maintaining the protective function against oxygen permeation, thus reducing structural complexity while preserving emission efficiency.
Solution Approach 2:
The wavelength conversion layer is designed to serve multiple functions: wavelength conversion, oxygen barrier protection, and structural support. By making the layer itself oxygen-resistant through specific material selection (polymerizable composition with low oxygen permeability), it performs both its primary function and the protective function simultaneously.
2Stability of the object's composition
If the wavelength conversion layer is made from a polymerizable composition with low oxygen permeability, then the brightness uniformity is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The invention changes the chemical composition parameters of the wavelength conversion layer by using a polymerizable composition with specific properties (LogP value of the polymerizable compound, composition ratios of quantum dots and dispersant). This parameter optimization achieves low oxygen permeability and bright uniformity while providing flexibility in manufacturing through standard polymerization processes.
3Reliability
If quantum dots are used to achieve high color reproducibility, then the color quality is improved, but the oxygen sensitivity increases
Solution Approach 1:
The invention converts the harmful effect of oxygen sensitivity into a beneficial design criterion. By recognizing that quantum dots are sensitive to oxygen, the invention deliberately creates an oxygen-barrier environment within the wavelength conversion layer itself, turning the vulnerability into a design feature that protects the quantum dots while maintaining color reproducibility.
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 suppresses the decrease in brightness in the outer peripheral regions of liquid crystal display devices, maintaining high image quality by reducing oxygen permeability and stabilizing quantum dots within the wavelength conversion layer.
Implementation Method 1
a wavelength conversion layer which is formed by curing the polymerizable composition
Implementation Method 2
white light can be realized using fluorescence which is emitted by excitation of two or three kinds of quantum dots having different light emitting properties
Implementation Method 3
a compound having a LogP value of 3.0 or lower is a compound having higher polarity than oxygen as a nonpolar molecule, and a wavelength conversion layer which is formed of a polymerizable composition including a large amount of the above-described compound has poor compatibility with oxygen
Data Source
AI summary
A polymerizable composition provides a high brightness and suppressed decrease in brightness in an outer peripheral region when used in a wavelength conversion member, a wavelength conversion member, a backlight unit, and a liquid crystal display device. The polymerizable composition includes quantum dots having surfaces coordinated with a ligand, a polymerizable compound, and a dispersant, in which the ligand is a molecule that includes a saturated hydrocarbon chain having 6 or more carbon atoms and a coordinating group, a LogP value of the polymerizable compound is 3.0 or lower, the dispersant has a nonpolar and a polar portion in a molecule, and the nonpolar portion is at least one selected from the group consisting of a saturated hydrocarbon chain having 6 or more carbon atoms, an aromatic ring, and a saturated aliphatic ring. The wavelength conversion member, the backlight unit, and the liquid crystal display device include the polymerizable composition.