Wavelength Conversion Member Refractive Index Gradient
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Solution Overview
Problem
Wavelength converters with high refractive index binder layers suffer from increased in-plane guided light, leading to reduced light extraction efficiency and power density due to larger output light spot diameters, especially when irradiated with high power density excitation light.
Innovation Solution
A wavelength conversion member with a substrate, phosphor particles, and a binder layer where the refractive index of the phosphor particles is higher than that of the binder layer, and a light reflecting film on the substrate interface, reducing in-plane guided light and enhancing light extraction efficiency and power density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a binder layer with high refractive index is used to hold phosphor particles, then the binder layer can effectively fix the phosphor particles, but the in-plane guided light increases and light extraction efficiency decreases
Solution Approach 1:
The patent changes the refractive index parameter of the binder layer from high (1.45-1.50 for silica) to low (below 1.40), which fundamentally alters the optical properties and reduces in-plane guided light while maintaining phosphor particle fixation capability
Solution Approach 2:
The patent applies different refractive index characteristics to different components: the binder layer has low refractive index to minimize guided light, while the light reflecting film has high reflectance to maximize light extraction, creating optimized local optical properties throughout the system
2Power
If high power density excitation light is used to improve light output, then the wavelength converter can achieve higher output, but in-plane guided light increases and output light spot diameter increases
Solution Approach 1:
The patent changes the optical parameter (refractive index) of the binder layer to reduce in-plane guided light formation, enabling the system to maintain high conversion efficiency even when irradiated with high power density excitation light
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 configuration results in improved light extraction efficiency and higher power density of output light, suitable for applications like illumination devices and projectors, by minimizing in-plane guided light and output light spot diameter.
Implementation Method 1
a wavelength converter including phosphor particles excited by excitation light
Implementation Method 2
a light reflecting film that reflects fluorescent light radiated by the phosphor particles
Data Source
AI summary
A wavelength conversion member includes: a substrate; a wavelength converter including phosphor particles excited by excitation light and a binder layer that fixes or adheres the adjacent phosphor particles to one another, the wavelength converter being provided on a front surface side of the substrate; and a light reflecting film that reflects fluorescent light radiated by the phosphor particles, the light reflecting film being provided on at least a part of an interface between the substrate and the wavelength converter, wherein a refractive index of the phosphor particles is larger than a refractive index of the binder layer. It is preferable that the binder layer include nanogaps which are voids with an average diameter of 300 nm or less in an inside.