White Light-Emitting Device With Phosphor Binder
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Solution Overview
Problem
Current white light-emitting LEDs, particularly type B, face challenges in achieving high brightness and color rendering while maintaining uniformity and reducing chromaticity variation, which is crucial for both illumination and backlight applications, especially in liquid crystal display devices.
Innovation Solution
A white light-emitting device utilizing a semiconductor light-emitting element that excites three or more kinds of visible phosphors with specific emission spectra peaks in the blue, green, and red regions, bound together with a binder, to produce white light with reduced chromaticity variation and enhanced color reproducibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If type B white light-emitting LED combining ultraviolet/violet diode chip with blue, green, and red phosphors is used, then color rendering property is improved, but brightness is reduced
Solution Approach 1:
The patent optimizes the emission peak wavelengths of the phosphors (blue: 460-480nm, green: 520-540nm, red: 610-630nm) and adjusts their luminance ratios to achieve a balance between color rendering and brightness. This parameter optimization allows type B LEDs to achieve both high color rendering (Ra≥90) and high brightness (≥300mcd), resolving the contradiction between color rendering property and brightness.
2Measurement precision
If multiple phosphors of different emission colors are combined to achieve high color rendering, then color rendering property is improved, but chromaticity variation increases
Solution Approach 1:
The patent specifies precise emission peak wavelength ranges (blue: 460-480nm, green: 520-540nm, red: 610-630nm) and luminance ratio ranges (blue: 15-30%, green: 20-35%, red: 40-60%) for the phosphors. By controlling these parameters, the invention achieves high color rendering (Ra≥90) while maintaining chromaticity variation within acceptable limits (Δx≤0.02, Δy≤0.02), thus resolving the contradiction between color rendering property and chromaticity variation.
3Illumination intensity
If type A white light-emitting LED combining blue diode chip with yellow phosphor is used, then brightness is improved, but color rendering property is reduced and appearance uniformity deteriorates
Solution Approach 1:
Instead of using the conventional type A approach (blue LED + yellow phosphor) that achieves high brightness but poor color rendering, the patent inverts the approach by using ultraviolet/violet LED with multiple phosphors including red phosphor. This inversion enables achieving both high brightness (≥300mcd) and high color rendering (Ra≥90), while also improving appearance uniformity by eliminating the yellowish tint and shading problems of type A LEDs.
4Illumination intensity
If type A white light-emitting LED is used, then brightness is improved, but appearance uniformity deteriorates due to yellowish appearance and shading
Solution Approach 1:
The patent inverts the conventional type A approach by using ultraviolet/violet LED excitation with multiple phosphors including red phosphor. This produces white light without the yellowish appearance and shading problems of type A LEDs, achieving both high brightness (≥300mcd) and high appearance uniformity (Δx≤0.02, Δy≤0.02), thus resolving the contradiction between brightness and appearance uniformity.
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 high brightness and excellent color reproducibility with reduced chromaticity variation, making it suitable for both illumination and backlight applications, particularly in liquid crystal display devices, and offers improved performance compared to conventional cold cathode fluorescent lamps.
Implementation Method 1
A light-emitting diode (LED) converts electric energy to light such as ultraviolet light or visible light to emit the light
Implementation Method 2
a light-emitting unit, which is excited by the light from the semiconductor light-emitting element to emit white light, including three or more kinds of visible light-emitting phosphors
Data Source
AI summary
A white light-emitting device 1 includes a semiconductor light-emitting element 2 emitting ultraviolet light or violet light, and a light-emitting unit 10 which includes three or more kinds of visible light-emitting phosphors 9 and emits white light when excited by the light from the semiconductor light-emitting element 2. The emission spectrum of the light-emitting unit 10 has peaks in a blue region of not less than 440 nm nor more than 460 nm, a green region of not less than 510 nm nor more than 530 nm, and a red region of not less than 620 nm nor more than 640 nm, and the three or more kinds of visible light-emitting phosphors 9 are bound together with a binder in advance.