Phosphate-Coated Nitride Phosphor for Higher Light Extraction
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Solution Overview
Problem
Existing fluorescent materials used in light emitting devices, such as those based on nitride compounds, face challenges in achieving high light emission intensity and efficiency due to limitations in refractive index differences and light extraction efficiency.
Innovation Solution
A fluorescent material comprising a nitride fluorescent material with lanthanum (La), cerium (Ce), silicon (Si), and nitrogen (N), and a first phosphorus compound, such as lanthanum phosphate, disposed on its surface, is developed. This material is produced through a heat treatment process at specific temperatures in the presence of a second phosphorus compound and water, forming a thin film that enhances light emission intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If heat treatment is applied to nitride fluorescent material in the presence of fluorine containing substance, then yellow fluorescent material can be produced, but light emission intensity and efficiency are insufficient due to refractive index limitations
Solution Approach 1:
The patent applies a phosphorus compound coating specifically on the surface of the nitride fluorescent material particles, creating a localized region with different optical properties. This surface coating has a refractive index intermediate between the nitride material and air, locally improving light extraction efficiency without changing the bulk material properties.
Solution Approach 2:
The patent creates a composite structure where a phosphorus compound (such as lanthanum phosphate) is disposed on the surface of the nitride fluorescent material. This composite approach combines the high efficiency of nitride materials with the optical benefits of phosphorus compounds to achieve improved light emission intensity and extraction efficiency.
2Illumination intensity
If phosphorus compound content is increased to improve light emission, then light emission intensity improves, but excessive phosphorus content degrades fluorescent properties
Solution Approach 1:
The patent precisely controls the phosphorus compound content within the range of 0.07-0.8 mass%, representing an optimized parameter that balances light emission enhancement with maintenance of fluorescent properties. This specific parameter range prevents phosphorus-induced degradation while maximizing the beneficial effects on light extraction and emission intensity.
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 resulting fluorescent material exhibits improved light emission intensity and efficiency, with a light emission peak wavelength in the range of 520 nm to 620 nm, and a half maximum full width of 100 nm to 150 nm, demonstrating enhanced performance in light emitting devices.
Implementation Method 1
applying heat treatment to a nitride fluorescent material having a composition represented by Formula (1) below at a temperature of 90° C. or higher and 400° C. or lower in the presence of a second phosphorus compound
Implementation Method 2
a light emitting device including a light emitting element that has a light emission peak wavelength in a wavelength range at 350 nm or more and 500 nm or less, and a wavelength converting member containing the fluorescent material
Data Source
AI summary
Provided is a fluorescent material with high brightness. The fluorescent material includes a nitride fluorescent material comprising La, Ce, Si, and N; and a first phosphorus compound disposed on a surface of the nitride fluorescent material. The first phosphorus compound includes at least one selected from the group consisting of lanthanum phosphate, lanthanum hydrogen phosphate, and hydrates thereof. A content of phosphorus atoms in the fluorescent material is 0.07% by mass or higher and 0.8% by mass or lower.