Quantum Dot Color Filter Ink With Blue-Absorbing Layers
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Solution Overview
Problem
Existing quantum dot color filters (QDCFs) in liquid crystal displays (LCDs) suffer from blue light leakage and limited external quantum efficiency (EQE) due to low optical density (OD) and re-absorption issues, particularly when using QDs with small absorption cross-sections in the blue region, leading to color contamination and reduced viewing angle.
Innovation Solution
Incorporating blue light-absorbing materials, such as organic dyes and luminescent materials, with quantum dots (QDs) in the QDCF layers to preferentially absorb blue light, reducing leakage and enhancing EQE, while using ink compositions containing di(meth)acrylate monomers, multifunctional crosslinking agents, and scattering particles for film formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the concentration of quantum dots is increased to achieve increased blue light absorption and optical density, then blue light absorption is improved, but re-absorption of emitted photons occurs causing reduction in external quantum efficiency
Solution Approach 1:
The QDCF layer is divided into multiple sub-layers with different quantum dot concentrations. The first sub-layer has a first concentration optimized for blue light absorption, while the second sub-layer has a second concentration optimized for minimizing re-absorption. This segmentation allows each sub-layer to perform its specific function effectively without the drawbacks of high concentration throughout the entire layer.
Solution Approach 2:
Different regions of the QDCF layer are given different local properties by varying the quantum dot concentration in different sub-layers. The first sub-layer is designed with higher concentration for strong blue light absorption, while the second sub-layer uses lower concentration to minimize re-absorption of emitted photons. This local differentiation resolves the contradiction between absorption strength and efficiency.
2Quantity of substance
If the thickness of the quantum dot layer is increased to achieve increased blue light absorption, then optical density is improved, but viewing angle is compromised due to parallax issues
Solution Approach 1:
The single thick QDCF layer is segmented into multiple thinner sub-layers. Each sub-layer has optimized thickness to maintain good viewing angles while collectively providing sufficient blue light absorption. This segmentation allows the system to achieve high optical density without the parallax issues associated with a single thick layer.
Solution Approach 2:
Instead of increasing thickness in one dimension to improve absorption, the solution distributes the absorption function across multiple sub-layers in the vertical dimension, with each sub-layer contributing to the overall absorption while maintaining optimal local thickness for viewing angle performance.
3Quantity of substance
If the concentration of quantum dots is increased to achieve increased blue light absorption, then optical density is improved, but color distortion occurs due to spectral red shift
Solution Approach 1:
The QDCF is divided into sub-layers with different quantum dot concentrations to prevent spectral red shift. The first sub-layer with higher concentration provides strong blue light absorption, while the second sub-layer with lower concentration prevents excessive re-absorption that would cause red shift. This segmentation maintains color accuracy while achieving high optical density.
Solution Approach 2:
The quantum dot concentration parameter is changed between different sub-layers to optimize both absorption and color accuracy. By varying this parameter spatially across the QDCF structure, the system achieves high blue light absorption without the spectral red shift that would result from uniformly high concentration throughout the entire layer.
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 reduces blue light leakage, improves color gamut, and enhances EQE by up to 40% in QDCFs, ensuring minimal blue light transmission through red and green sub-pixels, thereby maintaining color accuracy and display performance.
Implementation Method 1
a blue light-absorbing material, characterized in that it preferentially absorbs blue light relative to red light or green light
Implementation Method 2
the QDCF layer absorbs all or a portion of the incident blue photons from the BLU and converts at least a portion of the absorbed photons into green photons and red photons
Data Source
AI summary
Liquid ink compositions containing quantum dots for optoelectronic display applications are provided. Also provided are solid films formed by drying the ink compositions, optical elements incorporating the solid films, display devices incorporating the optical elements, and methods of forming the solid films, optical elements, and the devices. Liquid ink compositions and solid films made by drying the liquid ink compositions include one or more blue light-absorbing materials in combination with red light-emitting QDs or green light-emitting QDs.