Light-Emitting Device with Segmented Green Fluorescent Materials
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Solution Overview
Problem
Existing light-emitting devices for liquid crystal displays face limitations in achieving high color reproducibility and luminance due to the wide half bandwidth of β sialon fluorescent materials, which restricts the color reproduction range.
Innovation Solution
A light-emitting device comprising a light-emitting element with a peak emission wavelength between 400 nm to 470 nm, and a fluorescent member with specific compositions of first, second, and third fluorescent materials, optimizing the emission spectrum to have relative intensities at 500 nm and 540 nm of 35% or less, enhancing color purity and luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If β sialon fluorescent material is used to achieve high luminance, then luminous flux is improved, but color reproduction range deteriorates due to wide half bandwidth
Solution Approach 1:
The patent segments the green fluorescent material into two distinct materials: a first green fluorescent material with narrow half bandwidth (peak 510-530 nm) for color purity, and a second green fluorescent material with wide half bandwidth (peak 530-560 nm) for luminance. This segmentation resolves the contradiction by assigning different functional roles to each material, allowing both high color reproduction and high luminance to be achieved simultaneously.
Solution Approach 2:
The patent uses a composite fluorescent layer containing multiple fluorescent materials (first green, second green, and red fluorescent materials) with different emission characteristics. The composite structure combines the advantages of narrow-band materials (color purity) and wide-band materials (luminance), resolving the technical contradiction between color reproduction range and luminous flux.
2Illumination intensity
If green fluorescent material with wide emission spectrum is used, then luminance is improved, but color purity at green wavelength deteriorates
Solution Approach 1:
The green emission spectrum is segmented into two components: a narrow-band first green fluorescent material (510-530 nm peak) that provides color purity, and a wide-band second green fluorescent material (530-560 nm peak) that provides luminance. This segmentation allows each material to optimize for its specific function without compromising the other.
Solution Approach 2:
Different regions of the green spectrum are assigned different qualities: the first green fluorescent material provides high color purity in the 510-530 nm range, while the second green fluorescent material provides high luminance in the 530-560 nm range. This local quality differentiation resolves the contradiction between color purity and luminance.
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 device achieves improved color reproducibility and luminance, expanding the color reproduction range beyond conventional devices, particularly meeting high-definition standards like BT. 2020, with clear separation of colors through precise adjustment of the green wavelength region.
Implementation Method 1
A light-emitting device includes a light-emitting element and a fluorescent member. The light-emitting element has a peak emission wavelength in a range of from 400 nm to 470 nm
Implementation Method 2
The fluorescent member includes a first fluorescent material, a second fluorescent material, and a third fluorescent material
Data Source
AI summary
Provided is a light-emitting device including a light-emitting element having a peak emission wavelength in a range of from 400 nm to 470 nm, and a fluorescent member including a first fluorescent material including an aluminate that contains Mg, Mn, and at least one alkali earth metal selected from the group consisting of Ba, Sr, and Ca, a second fluorescent material having a different composition from the first fluorescent material, and a third fluorescent material. The first, second and third fluorescent materials have a peak emission wavelength in a range of from 510 nm to 525 nm, from 510 nm to 550 nm, and from 620 nm to 670 nm, respectively. The light-emitting device has an emission spectrum with a relative emission intensity of 35% or less at 500 nm and of 65% or less at 540 nm when a local maximum light-emitting emission intensity in a range of from 510 nm to 535 nm is taken as 100%.