Nitride Phosphor Surface Coating for LED Thermal Stability
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Solution Overview
Problem
Current white LED devices face challenges with high correlated color temperature and low color-rendering index due to the use of yellow phosphors, and suffer from poor thermal stability, leading to reduced light-emitting efficiency and shorter service life.
Innovation Solution
An inorganic nitride-based fluorescent material is developed by coating a metal oxide, metal hydroxide, or metal carbonate on a nitride-based fluorescent host material, enhancing luminance and thermal stability through a surface coating process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If yellow phosphor is used in white LED, then the LED can be manufactured with current technology, but the correlated color temperature becomes high and the color-rendering index becomes low
Solution Approach 1:
The patent uses a composite phosphor system combining nitride-based fluorescent material (emitting red light) with other phosphors to replace yellow phosphor. This composite approach enables warm white light with high color-rendering index while maintaining manufacturability through controlled co-firing or sequential coating processes.
2Illumination intensity
If nitride-based fluorescent material is used to improve color-rendering index, then the color-rendering index improves, but the thermal stability becomes poor due to thermal quenching
Solution Approach 1:
The patent applies a protective coating layer on the surface of nitride-based fluorescent particles, creating different properties in different regions: the core maintains red-light emission properties for high color-rendering index, while the surface coating provides thermal stability and protects against thermal quenching.
Solution Approach 2:
The protective coating acts as an intermediary between the nitride-based fluorescent material and the high-temperature environment. It mediates the thermal stress and prevents direct thermal damage to the fluorescent core, thereby improving thermal stability while preserving the red-light emission properties.
3Device complexity
If no protective coating is applied, then the manufacturing process is simple, but the service life is reduced due to poor thermal stability
Solution Approach 1:
The protective coating is applied in advance during the phosphor manufacturing process (co-firing or pre-coating before LED assembly). This preliminary protection prevents thermal degradation during LED operation, extending service life without adding significant complexity to the overall manufacturing workflow.
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 coated fluorescent material achieves improved luminance and thermal stability, extending the service life and performance of white LED devices while maintaining high light-emitting efficiency.
Implementation Method 1
an inorganic nitride-based fluorescent material in which a metal oxide, a metal hydroxide, or a metal carbonate is coated on a surface of a nitride-based fluorescent host material
Implementation Method 2
a nitride material that can produce red light can be applied as a phosphor. Since the nitride-based fluorescent material is capable of emitting a red-light broad band
Data Source
AI summary
The present invention relates to an inorganic nitride-based fluorescent material, comprising an inorganic fluorescent host material represented by the following formula (I):(M)xSiyNz:At (I)wherein, M is at least one metal selected from the group consisting of metals of IIA and IIIA, and x is from 1.0 to 3.0, and y is from 0.7 to 6.0, and z is from 1.0 to 9.0 and At is an activator; and a surface coating material is at least one metal oxide, metal hydroxide or metal carbonate, and the metal of the metal oxide, the metal hydroxide or the metal carbonate is selected from the group consisting of Mg, Ca, Sr, Ba, V, Cr, Mn, Fe, Co, Ni, Cu, La, Ga, In, Sn, Sb and Bi.