White LED Phosphor Composition for Stable High-CRI Light
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Solution Overview
Problem
White LEDs using ultraviolet to violet LEDs face challenges in maintaining emission intensity over long-term continuous lighting due to differences in phosphor characteristics, particularly with europium activated alkaline earth orthosilicate phosphors being susceptible to environmental factors.
Innovation Solution
A white LED configuration that combines an ultraviolet to violet LED with a cerium activated yttrium aluminum garnet-based phosphor and a blue phosphor, where the blue phosphor absorbs ultraviolet to violet light and converts it to blue light, which is then converted to green to yellow light by the YAG phosphor, resulting in a stable and reliable white light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If europium activated alkaline earth orthosilicate phosphor is used in ultraviolet to violet LED, then color rendering is improved, but emission intensity degrades over long-term continuous lighting
Solution Approach 1:
The patent changes the phosphor material parameters by switching from europium activated alkaline earth orthosilicate phosphor to cerium activated yttrium aluminum garnet-based phosphor. This material substitution maintains good color rendering properties while significantly improving emission intensity stability and resistance to environmental degradation during long-term operation.
Solution Approach 2:
The patent employs a composite phosphor system combining cerium activated yttrium aluminum garnet-based phosphor with blue phosphor materials. This composite approach leverages the complementary strengths of different phosphor materials to achieve both excellent color rendering and stable emission intensity over time.
2Illumination intensity
If blue LED is used with phosphors, then white light is obtained, but blue light hazards and poor color rendering occur
Solution Approach 1:
The patent extracts and eliminates the harmful blue light component by using ultraviolet to violet LED instead of blue LED. The ultraviolet to violet light excites the phosphors to produce white light without the harmful blue light peak, thereby removing the blue light hazard while maintaining white light output.
Solution Approach 2:
The patent converts the potentially harmful ultraviolet radiation into beneficial visible light through phosphor down-conversion. The ultraviolet to violet LED light, which could be harmful, is absorbed by the phosphors and converted to safe visible white light with good color rendering, turning a potential harm into a benefit.
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 configuration achieves high color rendering and maintains luminous flux effectively over long periods, reducing the degradation of emission intensity and minimizing blue light hazards, while providing white light with excellent reliability and health considerations.
Implementation Method 1
a blue phosphor, where the blue phosphor absorbs ultraviolet to violet light and converts it to blue light
Implementation Method 2
a cerium activated yttrium aluminum garnet-based phosphor and a blue phosphor, where the blue phosphor absorbs ultraviolet to violet light and converts it to blue light, which is then converted to green to yellow light by the YAG phosphor
Data Source
AI summary
According to one embodiment, a white light source includes a combination of a light emitting diode and phosphors. One of the phosphors is at least a cerium activated yttrium aluminum garnet-based phosphor, There is no light emission spectrum peak at which a ratio of a largest maximum value to a minimum value is greater than 1.9. The largest maximum value is largest among at least one maximum value present in a wavelength range of 400 nm to 500 nm in a light emission spectrum of white light emitted from the white light source. The minimum value is adjacent to the largest maximum value in a longer wavelength side of the light emission spectrum.