Red Phosphor for Natural White Light
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional red phosphors used in white LEDs have limited color rendering properties due to low half bandwidth and emission peak in the 550 nm to 700 nm wavelength band, making it difficult to achieve natural white light with sufficient luminous efficiency.
Innovation Solution
A red phosphor with a composition formula Az(Sr, M)2(Si, Al)O4−xNy, where A is lithium, potassium, or sodium, and M is barium, magnesium, or calcium, exhibiting a light emission peak between 600 nm and 700 nm, and including europium or dysprosium as an activator, with a spectrum half bandwidth of 83 nm to 150 nm, and a method involving mixing and sintering of raw materials followed by milling to enhance thermal and chemical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional red phosphors with emission peak at 550 nm to 700 nm are used, then the phosphor can be manufactured with existing technology, but the color rendering property is insufficient and natural white light cannot be achieved
Solution Approach 1:
The patent changes the emission wavelength parameter of the red phosphor from the conventional 550-700 nm range to a new range of 600-780 nm with peak emission at 610-780 nm. This parameter change enables sufficient color rendering properties and natural white light generation while maintaining compatibility with existing blue LED excitation sources (430-480 nm). The compositional parameters are also optimized with specific ratios of Sr, M, Si, Al, and activator concentrations to achieve the desired optical properties.
Solution Approach 2:
The patent employs a composite phosphor material system with the general formula A2(Sr, M)2(Si, Al)O4-xNy:R, combining multiple elements in specific proportions. The composite structure includes host lattice materials (Sr, M, Si, Al) and activator ions (R = Eu, Dy, or their combinations) to achieve enhanced color rendering properties. This composite approach allows simultaneous optimization of emission wavelength, half bandwidth (83-150 nm), and stability while maintaining ease of manufacture through conventional ceramic processing techniques.
2Manufacturing precision
If red phosphor with low half bandwidth is used, then the manufacturing process is simple, but the color rendering index is insufficient and desired natural white light cannot be implemented
Solution Approach 1:
The patent optimizes the half bandwidth parameter to a specific range of 83-150 nm, which is wider than conventional phosphors. This parameter change, combined with shifting the emission peak to 610-780 nm, achieves sufficient color rendering index (CRI > 80) and natural white light generation. The compositional parameters are controlled within specific ranges to maintain this half bandwidth while avoiding excessive complexity in the manufacturing process.
3Productivity
If conventional phosphors are used to manufacture white LEDs, then the device can be produced with current technology, but the luminous efficiency and color rendering are insufficient
Solution Approach 1:
The patent changes the emission wavelength parameter to 610-780 nm with peak at 610-780 nm and half bandwidth of 83-150 nm, which improves both luminous efficiency and color rendering quality simultaneously. This parameter optimization ensures high luminous efficiency by better matching the human eye's spectral sensitivity in the red region while achieving natural white light with CRI > 80, all while maintaining compatibility with existing blue LED excitation sources and conventional manufacturing processes.
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 red phosphor demonstrates improved luminance by 20% or more compared to silicate-based phosphors, achieving high color rendering properties and stability, enabling the production of white LEDs that emit light close to natural light using blue or ultraviolet excitation sources.
Implementation Method 1
A red phosphor and a phosphor of another color are used in combination... one or more phosphors selected from phosphors of red, blue, yellow and the like are applied to blue or ultraviolet LED chips
Implementation Method 2
a sintering step sinters the mixture to obtain a compound expressed in a composition formula
Data Source
AI summary
Provided is a red phosphor having superior thermal and chemical stability and excellent luminous efficiency, wherein the red phosphor comprises a compound expressed in the composition formula: Az(Sr, M)2(Si, Al)O4−xNy:R(0<x<3, y=2x/3, 0.001<z<0.1), where A is at least one element selected from a group consisting of lithium (Li), potassium (K) and sodium (Na), M is at least one element selected from a group consisting of barium (Ba), magnesium (Mg), and calcium (Ca), and R is at least one element selected from a group consisting of lanthanide and a transition metal element.