Barrier Film Refractive Index Stack for Humidity-Stable Color
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Solution Overview
Problem
Liquid crystal display devices using quantum dots in wavelength conversion sheets experience color instability due to changes in spectral transmission spectra caused by swelling of organic coating layers in high humidity environments, affecting the color purity and quality of the display.
Innovation Solution
A barrier film comprising specific refractive index relationships and layer configurations, including inorganic oxide and organic coating layers, is applied to wavelength conversion sheets to maintain color stability by controlling the spectral transmission spectrum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a barrier film with organic coating layer is used to protect quantum dot-containing layer, then protection against moisture and oxygen is improved, but color stability deteriorates due to swelling in high humidity environments
Solution Approach 1:
The patent applies parameter changes by precisely controlling the thickness of the organic coating layer (70-480 nm) and the optical path difference (Expression 1: d1 = (nB×tB + nD×tD)/λ0) to compensate for swelling effects. By optimizing these parameters, the barrier film maintains both protective function and color stability despite humidity-induced swelling.
Solution Approach 2:
The patent uses a composite barrier film structure combining inorganic oxide layers (Al2O3, SiO2, TiO2) with organic coating layers. This composite structure provides both moisture/oxygen barrier properties from the inorganic layers and controlled optical properties from the organic layers, resolving the contradiction between protection and color stability.
2Reliability
If the thickness of organic coating layer is increased to improve barrier properties, then protection against moisture and oxygen is improved, but color accuracy deteriorates due to excessive swelling
Solution Approach 1:
The patent establishes a specific thickness range for the organic coating layer (70-480 nm) that balances barrier properties and color accuracy. Within this range, the layer provides sufficient protection while limiting swelling-induced color shifts. The upper limit of 480 nm is specifically set to prevent excessive swelling that would degrade color accuracy.
Solution Approach 2:
The patent applies different material properties to different layers: the inorganic oxide layers provide dense barrier properties for moisture and oxygen blocking, while the organic coating layers provide controlled optical properties and additional protection. This local differentiation of material qualities optimizes both barrier performance and color stability.
3Device complexity
If a simple single-layer barrier film is used, then device complexity is reduced, but color stability deteriorates due to insufficient control of spectral transmission
Solution Approach 1:
The patent segments the barrier film into multiple functional layers: light-transmitting base material, inorganic oxide layer A, organic coating layer B, inorganic oxide layer C, and organic coating layer D. Each layer serves a specific function (structural support, barrier protection, optical control), and their combined effect stabilizes spectral transmission characteristics while maintaining manageable device complexity.
Solution Approach 2:
The patent employs a composite multi-layer structure combining different materials (PET base material, Al2O3/SiO2/TiO2 inorganic oxide layers, polyvinyl alcohol organic coating layers) with complementary properties. This composite structure provides both the barrier functionality and the optical control needed for color stability, overcoming the limitations of simple single-layer films.
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 barrier film effectively suppresses color changes in liquid crystal display devices, ensuring consistent color purity and quality over time by stabilizing the spectral transmission characteristics.
Implementation Method 1
it is preferable to protect the surfaces of both sides of a quantum dot-containing layer with a barrier film
Implementation Method 2
an organic coating layer of the barrier film swells to change the waveform of the spectral transmission spectrum of the barrier film
Implementation Method 3
The particle size of the quantum dot is smaller than the Bohr radius of an exciton of the compound semiconductor, and thus the quantum confinement effect appears
Implementation Method 4
a reflectance at an interface between the inorganic oxide layer A and the organic coating layer B is larger than a reflectance at an interface between the light-transmitting base material and the inorganic oxide layer A
Data Source
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AI summary
Provided is a barrier film that can suppress a change in color when applied to a wavelength conversion sheet. A barrier film for a wavelength conversion sheet, comprising an inorganic oxide layer A, an organic coating layer B, an inorganic oxide layer C, and an organic coating layer D in presented order on a light-transmitting base material; wherein refractive indexes of the inorganic oxide layer A, the organic coating layer B, the inorganic oxide layer C, and the organic coating layer D are defined as nA, nB, nc, and nD, respectively; thicknesses of the organic coating layer B and the organic coating layer D are defined as tB and tD, respectively; nA and nc are larger than nB and nD; and d1 represented by the following expression 1 represents a range of x ± 0.10 wherein x is an integer of 2 to 13. d1 = nB × tB/112.5 nm + nD × tD/112.5 nm (Expression 1)