Color Saturation Filter with Alternating Refractive Index Layers
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Solution Overview
Problem
Organic light-emitting diode (OLED) displays face challenges with decreasing emission efficiency and short lifespan of blue light-emitting materials, leading to poor color purity and reduced color gamut, making it difficult to accurately display full-color images.
Innovation Solution
A display apparatus with a color purity improving filter, comprising a substrate, OLEDs emitting different colors, and a filter with alternating layers of low and high refractive indexes, including a spacing layer, is used to enhance blue light color purity while maintaining high transmissivity for green and red light, reducing manufacturing costs and errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a conventional blue light-emitting material is used in OLED displays, then the device can emit blue light, but the emission efficiency decreases and the lifespan becomes short
Solution Approach 1:
The patent introduces a color purity improving filter as an intermediary component between the blue light-emitting material and the viewer. This filter has a transmissivity profile with FWHM of 100nm or less at the central wavelength, which purifies the blue light spectrum while allowing the OLED to continue using conventional blue light-emitting materials. The filter acts as a mediator that converts the broad-spectrum blue light into a narrow-band pure blue light, thereby improving color purity without requiring replacement of the unstable blue light-emitting materials.
2Manufacturing precision
If the color purity of blue light is improved using a narrow-band filter, then the color gamut increases, but the manufacturing complexity and cost increase
Solution Approach 1:
The patent achieves narrow-band filtering (FWHM ≤ 100nm) by precisely controlling the optical parameters of the filter layers. The first and second thin films are designed with specific refractive index differences and thickness ratios that create constructive and destructive interference patterns, resulting in a narrow transmission band. By adjusting the thickness parameters T1 and T2 of the layers, the filter achieves the desired spectral characteristics without requiring complex multi-layer structures or expensive materials.
3Manufacturing precision
If a color purity improving filter with narrow FWHM is used, then blue light color purity improves, but the transmissivity for green and red light must be maintained
Solution Approach 1:
The filter is designed with spatially varying optical properties through its multi-layer structure. The first thin film and second thin film have different refractive indexes and thickness configurations that create wavelength-selective transmission. The interference conditions are optimized such that only blue light wavelengths within the narrow FWHM range experience strong transmission, while green and red light wavelengths are transmitted through different optical paths with minimal absorption. This local optimization of transmission characteristics for different wavelength ranges allows simultaneous achievement of high blue light purity and high overall transmissivity.
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 improves blue light color purity, maintains high transmissivity for green and red light, and simplifies the manufacturing process, resulting in a display with enhanced color reproduction and reduced manufacturing complexity.
Implementation Method 1
a color purity improving filter, comprising a substrate, OLEDs emitting different colors, and a filter with alternating layers of low and high refractive indexes
Implementation Method 2
a filter with alternating layers of low and high refractive indexes
Data Source
AI summary
A display apparatus and a filter for improving color purity (color saturation filter) are disclosed. In one aspect, the display apparatus includes a substrate, a display device formed on the substrate and having a plurality of pixel areas that emit different colors of light, and a color saturation filter on the display device. The color saturation filter is formed with a substantially uniform thickness over the plurality of pixel areas and has a transmissivity such that a full width at half maximum at the central wavelength of blue light emitted from one of the pixel areas is about 100 nm or less.