Phosphor Matrix Refractive Index Optimization for Light Extraction
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Solution Overview
Problem
The existing ceramic composite wavelength conversion members in projectors do not adequately consider reabsorption of fluorescence and backscattering characteristics of excitation light, leading to insufficient light extraction efficiency.
Innovation Solution
A phosphor with a garnet structure, specifically YAG:Ce, is used in conjunction with a matrix phase of aluminum nitride (AlN) having a higher refractive index than the phosphor, and a controlled Ce/Y ratio of 0.0002 to 0.005 to optimize absorption and reduce backscattering, along with a reflective or transmissive configuration to enhance light extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the Ce/Y ratio in YAG phosphor is increased to improve light absorption, then the absorption of excitation light is enhanced, but the reabsorption of fluorescence increases and light extraction efficiency decreases
Solution Approach 1:
The patent optimizes the Ce/Y ratio parameter within a specific range (0.005 to 0.05) to achieve the best balance between excitation light absorption and fluorescence reabsorption. This parameter optimization resolves the contradiction by finding the optimal point where light absorption is sufficient while fluorescence extraction efficiency is maximized
Solution Approach 2:
The patent uses a composite ceramic structure consisting of a transparent ceramic matrix (such as Al2O3, MgAl2O4, or MgO) containing YAG:Ce phosphor particles. This composite material approach allows the matrix to provide mechanical support and thermal management while the phosphor particles perform light conversion, resolving the contradiction between absorption and extraction efficiency
2Productivity
If the phosphor phase content is increased to improve fluorescence output, then the light conversion capability is enhanced, but the backscattering of excitation light increases and light extraction efficiency decreases
Solution Approach 1:
The patent employs a composite ceramic material where phosphor particles are dispersed in a transparent ceramic matrix. The matrix phase (with refractive index different from phosphor) reduces backscattering of excitation light while the phosphor phase provides fluorescence conversion. This composite structure resolves the contradiction between high phosphor content for fluorescence output and low backscattering for light extraction efficiency
Solution Approach 2:
The patent creates a heterogeneous structure where phosphor particles are distributed within the transparent matrix, giving different local regions different functions: phosphor regions for light conversion and matrix regions for light transmission and reduced backscattering. This local quality differentiation resolves the contradiction between fluorescence output and backscattering loss
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 significantly increases the amount of extracted fluorescence, improves quantum yield, and maintains high thermal conductivity for efficient heat dissipation, resulting in enhanced light conversion efficiency and display quality in projectors.
Implementation Method 1
a phosphor phase made of A3B5O12:Ce having a garnet structure... configured to convert an incident excitation light into fluorescence
Implementation Method 2
a matrix phase having a refractive index higher than a refractive index of the phosphor phase
Implementation Method 3
a reflective layer provided at an opposite side of a light incident side of the phosphor from and configured to reflect the excitation light and the fluorescence
Data Source
AI summary
A phosphor includes a phosphor phase made of A3B5O12:Ce having a garnet structure and a matrix phase having a refractive index higher than a refractive index of the phosphor phase. A ratio of Ce to A in terms of number of atoms is 0.0002 or more and 0.005 or less. A is at least one selected from the group consisting of Lu, Gd, Tb, Ga, and Y. B is Al.