Concave Phosphor Particle Surfaces for Higher Fluorescence Output
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Solution Overview
Problem
The existing methods for increasing absorptance in single-crystal phosphor particles, such as etching with hydrofluoric acid, result in convexly curved surfaces that hinder the emission of fluorescence, leading to reduced intensity from phosphor-containing members in devices like projectors.
Innovation Solution
A phosphor particle with a concave portion on its surface, sized between 0.1 and 10 times the wavelength of the fluorescence, and a wavelength conversion element with a phosphor layer bound by glass, which is calcined at a temperature higher than the glass's softening point to optimize the binding area and reduce light scattering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the surface of single-crystal phosphor particles is etched with hydrofluoric acid to increase absorptance, then the absorptance of excitation light is improved, but the emission intensity of fluorescence is reduced due to convexly curved surfaces hindering light emission
Solution Approach 1:
The patent inverts the conventional etching approach by creating concave portions instead of convexly curved surfaces. This inversion allows the surface to both absorb excitation light effectively and emit fluorescence efficiently, resolving the contradiction between absorptance and emission intensity
Solution Approach 2:
The patent applies local quality by creating specific concave portions at predetermined positions on the phosphor particle surface. These localized concave structures optimize both light absorption and emission properties at different surface regions, maintaining high absorptance while enabling efficient fluorescence emission
2Strength
If the binding area between phosphor particles is increased to improve structural stability, then the mechanical strength is improved, but light scattering increases reducing optical efficiency
Solution Approach 1:
The patent applies local quality by providing the binder only at specific predetermined positions between phosphor particles rather than uniformly across all surfaces. This localized binding maintains structural stability while minimizing light scattering, as the binder is placed in regions where it does not interfere with optical paths
Solution Approach 2:
The patent segments the binding function by providing discrete binder portions at specific positions rather than continuous binding. This segmentation allows structural stability to be maintained at critical points while leaving other regions free for optimal optical performance
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 enhances the emission intensity of fluorescence, reduces light absorption, and increases the internal quantum yield, leading to improved brightness and light use efficiency in optical systems like projectors.
Implementation Method 1
a phosphor particle configured to emit fluorescence longer in wavelength than excitation light entering the phosphor particle
Implementation Method 2
reflection of light by the surface is reduced to increase the absorptance
Implementation Method 3
a binder configured to bind a part of a surface of one of the phosphor particles adjacent to each other out of the plurality of the phosphor particles and a part of a surface of another of the phosphor particles to each other, and a substrate provided with the phosphor layer, wherein the binder includes glass
Implementation Method 4
calcining the mixture applied to the substrate at a calcination temperature 100° C. or more higher than a softening point of the glass
Data Source
AI summary
A phosphor particle is configured to emit fluorescence longer in wavelength than excitation light entering the phosphor particle. The phosphor includes a concave portion which is no smaller than 0.1 times as large as the wavelength of the fluorescence and no larger than 10 times as large as the wavelength of the fluorescence. The concave portion is disposed on a surface of the phosphor particle.