Phosphor Mixture for Consistent LED Color Temperature
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Solution Overview
Problem
Mass-producing white LEDs with consistent color temperature is challenging due to variations in phosphor distribution, leading to inefficient yield and color rendering issues in LED-based lamps.
Innovation Solution
The use of a phosphor-containing material with a fixed ratio of red and green phosphors disposed over blue LEDs, varying in thickness to achieve light emission along the Planckian locus in a chromaticity diagram, ensuring consistent color temperature and improved yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If white LEDs are mass-produced using conventional phosphor methods, then production volume increases, but color temperature consistency deteriorates
Solution Approach 1:
The patent changes the phosphor composition parameters by using a specific combination of red phosphor (K2SiF6:Mn4+) and green phosphor (β-SiAlON:Eu2+) in fixed weight ratios between 1:4 and 1:6. This parameter change ensures that variations in phosphor layer thickness result in color temperature variations along the Planckian locus rather than across the chromaticity diagram, maintaining color consistency during mass production.
Solution Approach 2:
The patent uses a composite phosphor material system combining two different phosphor types with complementary emission spectra. The red phosphor provides long-wavelength emission while the green phosphor fills the middle wavelength range, creating a composite material that maintains stable color rendering and temperature characteristics when applied in varying thicknesses over blue LED chips.
2Productivity
If phosphor distribution varies during manufacturing, then production efficiency improves, but color rendering performance deteriorates
Solution Approach 1:
The patent modifies the phosphor mixture parameters by selecting specific weight ratios of red to green phosphor (1:4 to 1:6), which changes the system's response to thickness variations. This parameter optimization ensures that even with inconsistent phosphor distribution during manufacturing, the emitted light maintains reliable color rendering with CRI≥90 and R9≥95.
3Manufacturing precision
If more phosphor bins are used to achieve consistent color temperature, then color quality improves, but manufacturing complexity and cost increase
Solution Approach 1:
The patent changes the fundamental parameter of phosphor composition to red and green phosphors in specific ratios, which transforms the color temperature response characteristic. This allows LEDs with varying phosphor thicknesses to fall within acceptable color temperature ranges with fewer bins, reducing the complexity from potentially dozens of bins to just 3-5 bins while maintaining color consistency.
4Reliability
If phosphor thickness is increased to improve color rendering, then CRI improves, but color temperature control becomes more difficult
Solution Approach 1:
The patent employs a composite phosphor system where red phosphor (K2SiF6:Mn4+) and green phosphor (β-SiAlON:Eu2+) work together in specific proportions. This composite material configuration ensures that increasing phosphor thickness enhances color rendering by providing complete spectral coverage while the specific composition ratio maintains color temperature stability along the Planckian locus.
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
This approach results in increased yield and improved color rendering performance by maintaining light distribution along the Planckian locus, allowing for consistent color temperature and higher CRI, making it easier to achieve target CRI values like 90.
Implementation Method 1
preparing a phosphor-containing material comprising a matrix material having dispersed therein a mixture of a red phosphor and a green phosphor... disposing different thicknesses of the phosphor-containing material on different ones of the LED chips
Data Source
AI summary
A method for fabricating light-emitting devices includes obtaining a plurality of light-emitting diode (LED) chips fabricated to emit blue light and preparing a phosphor-containing material comprising a matrix material having dispersed therein a mixture of a red phosphor and a green phosphor in a fixed ratio to each other. The method also includes disposing different thicknesses of the phosphor-containing material on different ones of the LED chips. The fixed ratio is chosen such that LED chips having different thicknesses of the phosphor-containing material emit light characterized by different points along the Planckian locus in a CIE chromaticity diagram.