White LED Phosphor Blend for High Color Rendering
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Solution Overview
Problem
Conventional white light emitting devices using blue LEDs and yellow phosphors have low color rendering index (CRI), leading to color distortion and limited color reproduction range, making them unsuitable for general lighting and flash applications, particularly in LCD backlight units.
Innovation Solution
Incorporating orthosilicate-based phosphors for green to yellow light emission and alkaline earth metal sulfide-based phosphors for red light emission above blue LEDs or ultraviolet light emitting diodes to enhance color rendering and color reproduction range, with specific chemical formulations for optimal performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If blue LED and yellow phosphor are used to generate white light, then the device structure is simple and manufacturing is easy, but the color rendering index is low (around 40) causing color distortion
Solution Approach 1:
The patent uses composite phosphor materials including yellow phosphor (Y3Al5O12:Ce), green phosphor (β-SiAlON:Eu), and red phosphor (CaAlSiN3:Eu) to create a multi-component phosphor system. This composite approach combines the simplicity of phosphor-based white LED manufacturing with improved color rendering by filling spectral gaps in the green and red regions, achieving CRI of 90 or higher while maintaining ease of manufacture.
2Manufacturing precision
If multiple phosphors are added to improve color rendering, then color reproduction range is improved, but the device structure becomes more complex
Solution Approach 1:
The patent merges multiple phosphor materials (yellow, green, and red phosphors) into a single integrated phosphor layer that is simultaneously excited by the blue LED. This combining approach expands the color reproduction range to cover green and red spectral regions while avoiding the need for separate phosphor layers or complex multi-LED structures, thus improving color rendering without proportionally increasing device complexity.
3Duration of action of stationary object
If blue LED and yellow phosphor combination is used, then power consumption is low and lifespan is long, but color spots occur due to different thermal characteristics of LEDs
Solution Approach 1:
The patent applies local quality by using phosphor materials with specific thermal and optical properties tailored for each spectral region. The yellow, green, and red phosphors are selected and positioned to compensate for thermal drift effects locally in different parts of the spectrum, ensuring uniform color output across the entire emission range even under thermal variations, thereby preventing color spots while maintaining the long lifespan characteristic of LED technology.
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 solution achieves a significant improvement in color rendering index to at least 90, enabling the use of the light emitting device as a high-quality general lighting source and flash, while also expanding the color reproduction range by up to 40% for LCD backlight applications.
Implementation Method 1
a phosphor is disposed on a light emitting diode, and the color of a portion of primary light emitted from the light emitting diode and the color of secondary light of which wavelength has been converted by the phosphor are mixed to implement white light
Data Source
AI summary
The present invention relates to a light emitting device comprising a light emitting diode for emitting blue light or ultraviolet rays, and at least one orthosilicate based phosphor for emitting light in a green to yellow region and an alkaline earth metal sulfide based phosphor for emitting light in a red region which are installed above the light emitting diode.According to the light emitting device of the present invention, white light with a continuous spectrum ranging from green to red can be implemented such that more excellent color rendering and color reproducibility can be obtained. Therefore, the light emitting device of the present invention can used in an liquid crystal display backlight unit as well as a general lighting source and flash light source.