White LED Lamp Using Rare Earth Borate Phosphor for Color Rendering
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Solution Overview
Problem
Current white LED lamps using ultraviolet excitation sources suffer from inadequate color rendering properties due to a lack of yellow components, particularly when using conventional green phosphors like LaPO4:Ce, Tb, which do not emit light effectively under long-wavelength ultraviolet excitation, and alternative phosphors like (Ba, Mg) Al10O17 provide insufficient yellow emission, leading to inferior color reproduction.
Innovation Solution
A white LED lamp incorporating a semiconductor light emitting element with a peak wavelength between 300-430 nm, a transparent resin layer, and a phosphor layer containing a rare earth borate phosphor activated by trivalent cerium and terbium, represented by the formula (R1-x-y)CexTbyBO3, where R is Sc, Y, La, Gd, or Lu, and x and y are within specific ranges, enhancing the green phosphor's ability to emit yellow components and improve color rendering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional green phosphors like LaPO4:Ce, Tb are used in ultraviolet excitation white LED lamps, then the structure is simple and manufacturing is easy, but the phosphor does not emit light effectively under long-wavelength ultraviolet excitation (300-430 nm), resulting in insufficient yellow emission and poor color rendering
Solution Approach 1:
The patent changes the chemical composition parameters of the green phosphor by substituting rare earth elements (Sc, Y, La, Gd, Lu) into the LaPO4 structure and co-activating with Ce and Tb, which modifies the phosphor's excitation characteristics to respond effectively to long-wavelength ultraviolet light while maintaining ease of manufacture through standard solid-state synthesis methods
Solution Approach 2:
The patent creates a composite phosphor material combining multiple rare earth elements (Sc, Y, La, Gd, Lu) with Ce and Tb activators in a phosphate matrix, resulting in a material that simultaneously achieves effective UV excitation response, strong yellow emission, and improved color rendering properties
2Illumination intensity
If alternative green phosphors like (Ba, Mg) Al10O17 are used to achieve emission under ultraviolet excitation, then the phosphor emits light under UV excitation, but the emission wavelength is around 515 nm which lacks yellow components, resulting in insufficient color rendering property
Solution Approach 1:
The patent modifies the emission spectrum parameters by adjusting the rare earth element composition and activator ratios, shifting the emission peak from 515 nm (green) to include significant yellow components around 560-580 nm, thereby improving color rendering while maintaining high emission intensity under UV excitation
3Illumination intensity
If blue emitting LED (460-480 nm) and yellow phosphor are combined to create white LED lamp, then the brightness characteristic is superior, but the color rendering property is inferior due to lack of red component
Solution Approach 1:
The patent merges multiple phosphor types (yellow-emitting Y3Al5O12:Ce, green-emitting rare earth borate:Ce,Tb, and red-emitting CaAlSiN3:Eu) into a single phosphor layer system excited by ultraviolet LED, combining their emission spectra to achieve full-color white light with superior color rendering while maintaining high brightness
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 significantly enhances the color rendering property of white LED lamps by increasing yellow emission, resulting in improved brightness and color reproducibility, making them suitable for illuminating devices as a potential replacement for conventional fluorescent lamps.
Implementation Method 1
A light emitting diode (LED) is a semiconductor light emitting element that converts electric energy into ultraviolet light and visible light to emit the light
Implementation Method 2
a phosphor layer, disposed on the transparent resin layer, emitting white light by being excited by the light emitted from the semiconductor light emitting element
Data Source
AI summary
A white light emitting lamp 1 includes a phosphor layer 5 which emits white light by being excited by light emitted from a semiconductor light emitting element 2. A transparent resin layer 4 is interposed between the semiconductor light emitting element 2 and the phosphor layer 5. The phosphor layer 5 contains, as a green phosphor, a rare earth borate phosphor activated by trivalent cerium and terbium.