β-Sialon Phosphor Powder Aggregation Control for Brighter White LEDs
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Solution Overview
Problem
The demand for higher brightness in white LEDs has increased, and existing β-type sialon phosphors do not effectively improve brightness due to inadequate control over the aggregation state of phosphor particles after ultrasonic homogenizer treatment.
Innovation Solution
A phosphor powder with EU-activated β-type sialon particles, where the median diameter ratio before and after ultrasonic homogenizer treatment is controlled between 1.05 and 1.70, is used to improve the brightness of white LEDs by optimizing the aggregation state of the phosphor particles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional β-type sialon phosphors are used without controlling aggregation state, then the phosphor can be easily manufactured, but the brightness of white LED is insufficient
Solution Approach 1:
The invention changes the particle size distribution parameters by controlling the aggregation state. Specifically, it defines a target particle size distribution where D10=5-15 μm, D50=15-30 μm, and D90=30-60 μm, and controls the aggregation state by adjusting the ratio D1/D2 to be 1.05-1.70. This parameter control approach enables improved LED brightness while maintaining manufacturability through standardized measurement and control methods.
Solution Approach 2:
The invention performs preliminary classification and aggregation control of phosphor particles before they are incorporated into LED packages. By pre-adjusting the particle size distribution and aggregation state to meet specific targets, the phosphor powder is optimized for maximum brightness performance before application, ensuring consistent high-performance results in the final LED product.
2Illumination intensity
If phosphor particles are highly dispersed, then the brightness increases, but the aggregation state becomes difficult to control
Solution Approach 1:
The invention implements a feedback control mechanism by establishing clear measurement standards and target ranges for particle size distribution and aggregation state. The D1/D2 ratio serves as a feedback parameter to monitor and adjust the aggregation state. By measuring actual particle sizes and comparing them against target ranges (D10=5-15 μm, D50=15-30 μm, D90=30-60 μm), manufacturers can adjust processing conditions to achieve optimal dispersion and brightness.
3Ease of operation
If the particle size is reduced to improve dispersibility, then the dispersibility improves, but the brightness may decrease due to insufficient light absorption
Solution Approach 1:
The invention applies local quality by creating a non-uniform particle size distribution rather than using uniformly fine particles. The distribution is optimized with D10=5-15 μm, D50=15-30 μm, and D90=30-60 μm, creating a mix of particle sizes where smaller particles fill gaps between larger ones, improving dispersibility while larger particles provide sufficient light absorption. This multi-scale approach optimizes both dispersibility and brightness simultaneously.
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 controlled aggregation state of the phosphor powder enhances the brightness and luminous flux of white LEDs, while maintaining improved dispersibility and suppressing brightness decrease, making it suitable for high-performance LED applications.
Implementation Method 1
the dispersion liquid is irradiated with ultrasonic waves for 3 minutes at a frequency of 19.5 kHz, and an output of 150 W
Implementation Method 2
a nitride phosphor or an oxynitride phosphor having a relatively stable crystal structure is attracting attention. In particular, since EU-activated β-type sialon phosphors have characteristics of excellent heat resistance and durability, and a small change in brightness with increasing temperature and also are excited by a wide range of wavelengths of ultraviolet to blue light and emits green light
Data Source
AI summary
A phosphor powder contains an EU-activated β-type sialon phosphor particles. When a median diameter in the phosphor powder having not been subjected to an ultrasonic homogenizer treatment is set as D1 and a median diameter in the phosphor powder having been subjected to an ultrasonic homogenizer treatment is set as D2, 1.05≤D1/D2≤1.70. A dispersion liquid in which 30 mg of the phosphor powder is uniformly dispersed in 100 ml of a 0.2% concentration of a sodium hexametaphosphate aqueous solution is added to a columnar container of which a bottom surface has an inner diameter of 5.5 cm. Then, the dispersion liquid is irradiated with ultrasonic waves for 3 minutes at a frequency of 19.5 kHz, and an output of 150 W, in a state where a cylindrical tip, which has an outer diameter of 20 mm, of an ultrasonic homogenizer is immersed in the dispersion liquid in ≥1.0 cm.