Sintered Phosphor-Composite Fluoride Binder Void Control
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Solution Overview
Problem
Conventional sintered phosphor-composites for LEDs suffer from insufficient internal quantum efficiency, poor temperature properties, and low thermal conductivity due to issues like light scattering, solid solution substitution, and amorphous binders leading to heat radiation inefficiencies.
Innovation Solution
A sintered phosphor-composite is developed using a nitride phosphor and a fluoride inorganic binder with controlled voids and grain sizes, reducing light scattering and maintaining high internal quantum efficiency, and utilizing a fluoride binder with a cubic crystal system to enhance transparency and thermal conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a YAG sintered phosphor-composite is prepared by firing only YAG powder at 1300°C, then the phosphor can be sintered, but light scattering is insufficient and separation between blue light and yellow light occurs, resulting in non-uniform light
Solution Approach 1:
The patent uses a composite material system consisting of YAG phosphor particles dispersed in a fluoride inorganic binder matrix. This composite structure allows the binder to provide mechanical strength while the phosphor particles provide luminescence function, resolving the contradiction between sintering strength and light uniformity by separating structural and functional roles.
Solution Approach 2:
The fluoride inorganic binder acts as an intermediary material that facilitates proper light scattering and transmission. It mediates between the phosphor particles and the external environment, enabling uniform light distribution while maintaining structural integrity during sintering.
2Ease of manufacture
If an amorphous glass binder is used in the sintered phosphor-composite, then the composite can be formed, but thermal conductivity is low and heat radiation efficiency is poor
Solution Approach 1:
The patent changes the physical state parameter of the binder from amorphous to crystalline. This parameter change dramatically improves thermal conductivity while maintaining formability, as crystalline structures provide better heat transfer pathways compared to amorphous structures.
Solution Approach 2:
The patent applies local quality by using a crystalline binder specifically in regions where high thermal conductivity is needed, while maintaining the overall composite structure. The crystalline binder provides localized heat dissipation pathways without compromising the forming ease of the overall composite.
3Ease of manufacture
If oxide phosphor and fluoride inorganic binder are sintered together, then the composite can be formed, but solid solution substitution occurs forming oxyfluoride, leading to decreased internal quantum efficiency
Solution Approach 1:
The patent changes the chemical composition parameter by selecting specific fluoride binders that are resistant to solid solution substitution with oxide phosphors. This parameter change prevents the formation of oxyfluoride and maintains high internal quantum efficiency while still enabling composite formation.
Solution Approach 2:
The patent uses a fluoride inorganic binder that copies the desirable properties of glass binders (formability, low melting point) while avoiding their detrimental effects (solid solution substitution, low thermal conductivity). The binder replicates the beneficial forming characteristics without the harmful chemical reactions.
4Device complexity
If the number of voids in the sintered phosphor-composite is not controlled, then the sintering process is simpler, but light scattering increases and internal quantum efficiency decreases
Solution Approach 1:
The patent changes the void content parameter to an optimal range (0.1-5% by volume) through controlled sintering conditions. This parameter optimization balances light scattering and internal quantum efficiency without requiring overly complex sintering processes.
Solution Approach 2:
The patent implements feedback control by monitoring void content during sintering and adjusting sintering parameters accordingly. This feedback mechanism ensures void content remains within the optimal range for maximizing internal quantum efficiency while maintaining process simplicity.
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 results in a sintered phosphor-composite with high internal quantum efficiency, improved heat resistance, and enhanced thermal conductivity, leading to increased brightness and stability in light-emitting devices with reduced brightness changes and color deviations under varying conditions.
Implementation Method 1
light scattering is insufficient, and separation between blue light from an LED and yellow from the phosphor occurs
Implementation Method 2
utilizing a fluoride binder with a cubic crystal system to enhance transparency
Implementation Method 3
enhanced thermal conductivity, leading to increased brightness and stability in light-emitting devices with reduced brightness changes and color deviations
Implementation Method 4
a YAG (yttrium-aluminum-garnet) phosphor that converts the blue light into yellow
Implementation Method 5
the sintered phosphor-composite absorbs at least part of light from the light source to emit light having a different wavelength
Implementation Method 6
a sintered phosphor-composite comprising a phosphor and a crystalline inorganic binder
Implementation Method 7
controlled voids and grain sizes, reducing light scattering and maintaining high internal quantum efficiency
Data Source
AI summary
A sintered phosphor-composite having a high internal quantum efficiency and a high transmittance is provided. The object can be achieved with a sintered phosphor-composite including a nitride phosphor and a fluoride inorganic binder, wherein, in cross-sectional observation, the sintered phosphor-composite includes at least a portion in which voids of not more than 1 μm are present in a number of not more than 700 within a cross-sectional area of 0.046 mm2, or a portion having a void area fraction of not more than 3% within a cross-sectional area of 0.046 mm2.