Light Emitting Device Phosphor Secondary Particle Structure
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Solution Overview
Problem
Existing light emitting devices face issues with insufficient light output and excitation purity, particularly in emitting green light with high efficiency.
Innovation Solution
A light emitting device comprising a first light emitting element with a peak emission wavelength of 430 nm to 490 nm, covered by a first phosphor with a peak emission wavelength of 490 nm to 570 nm, where the phosphor constitutes 50 weight % or greater of the covering member, and contains secondary particles, enhancing light output and excitation purity by mixing blue light from the element with green light emitted by the phosphor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a light emitting element with peak emission wavelength of 360 nm or greater and less than 480 nm is used with a fluorescent substance to emit green light, then green light emission is achieved, but the light output and excitation purity become insufficient
Solution Approach 1:
The patent changes the emission wavelength parameter of the light emitting element from the conventional 360-480 nm range to a more specific 430-490 nm range, and adjusts the phosphor emission wavelength to 490-570 nm. This parameter optimization enables simultaneous achievement of high light output and excitation purity of 60% or more.
Solution Approach 2:
The patent uses a composite structure consisting of a light emitting element combined with a phosphor-containing covering member. The covering member contains phosphor particles dispersed in a resin, creating a composite material system that converts the blue light from the LED to green light with improved excitation purity.
2Reliability
If phosphor content is increased to improve excitation purity, then excitation purity improves, but light output may be reduced due to increased absorption losses
Solution Approach 1:
The patent optimizes the phosphor content parameter to be 50 weight % or greater in the covering member, which balances the competing requirements of high excitation purity and maintained light output. This specific parameter setting ensures sufficient phosphor for pure excitation while avoiding excessive absorption losses.
Solution Approach 2:
The patent applies different properties to different parts of the covering member: the phosphor particles provide high excitation purity in the green light emission region, while the resin matrix maintains light transmission. This local differentiation of material properties resolves the contradiction between purity and output.
3Ease of manufacture
If primary particles only are used in phosphor, then manufacturing is simpler, but light diffusion and absorption efficiency are reduced
Solution Approach 1:
The patent segments the phosphor structure into primary particles and secondary particles (aggregates). This segmentation creates a hierarchical structure where primary particles maintain manufacturing simplicity while secondary particles provide enhanced light diffusion and absorption efficiency, resolving the contradiction between ease of manufacture and performance.
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 high light output and excitation purity, improving color reproducibility and reducing blue component emission, with the phosphor's secondary particles increasing absorption efficiency and surface area for enhanced light diffusion.
Implementation Method 1
a first phosphor having a peak emission wavelength in a range at 490 nm and 570 nm or less... light emitted from the first phosphor
Implementation Method 2
the first covering member covers the first light emitting element, and contains a first phosphor... light emitted from the first phosphor are mixed
Data Source
AI summary
A light emitting device includes a first light emitting element and a first covering member. The first light emitting element has a peak emission wavelength in a range of 430 nm or greater and less than 490 nm. The first covering member covers the first light emitting element, and contains a first phosphor having a peak emission wavelength in a range of 490 nm and 570 nm or less. A content of the first phosphor is 50 weight % or greater with respect to a total weight of the first covering member. A mixed color light in which light emitted from the first light emitting element and light emitted from the first phosphor are mixed has an excitation purity of 60% or greater on a 1931CIE chromaticity diagram. The first phosphor contains secondary particles.