Garnet Phosphor with High Refractive Index Matrix for Projectors

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Solution Overview

Problem

Existing ceramic composites used in wavelength conversion for projectors face challenges in improving fluorescence extraction efficiency, despite enhanced thermal conductivity.

Innovation Solution

A phosphor body with a phosphor phase of A3B5O12:Ce having a garnet structure and a matrix phase with a higher refractive index, where the phosphor phase content is between 56 vol % and 70 vol %, and the Ce to A ratio is between 0.004 and 0.04, is used. The phosphor body has a thickness of 45 μm to 150 μm and includes a matrix phase made of AlN for enhanced thermal conductivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If a ceramic composite is used with high thermal conductive filler to improve thermal conductivity, then thermal conductivity is improved, but fluorescence extraction efficiency cannot be sufficiently improved

Engineering Contradiction:

Improvethermal conductivityVSAvoidfluorescence extraction efficiency

Core Design Contradiction:

TemperatureVSProductivity

Solution Approach 1:

The patent uses a composite material consisting of YAG:Ce phosphor particles dispersed in a transparent ceramic matrix (Al2O3, MgAl2O4, or MgO). This composite structure allows simultaneous optimization of thermal conductivity (through the ceramic matrix) and fluorescence extraction efficiency (through the phosphor phase composition and distribution), resolving the contradiction between thermal management and optical performance

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent optimizes specific parameters including Ce concentration (0.03-0.15 atomic ratio), phosphor particle size (5-20 μm), and sintering conditions to achieve both high thermal conductivity and high fluorescence extraction efficiency. By precisely controlling these parameters, the composite achieves improved thermal conductivity while maintaining or enhancing optical performance

Inventive Principle:

Principle #35Parameter changes

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 effectively enhances the external quantum efficiency of fluorescence, prevents re-absorption, and balances thermal conductivity and quantum efficiency, leading to improved fluorescence extraction efficiency and bright fluorescence generation.

Implementation Method 1

a phosphor phase formed of A3B5O12:Ce having a garnet structure... configured to convert incident excitation light into fluorescence

Methodology Applied

Scientific EffectPhotoluminescence: Photoluminescence

Implementation Method 2

a matrix phase having a refractive index higher than that of the phosphor phase

Methodology Applied

Scientific EffectRefraction: Refraction

Implementation Method 3

a matrix phase made of AlN for enhanced thermal conductivity

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentUS20250155092A1Phosphor, wavelength conversion device, illumination device, and projector

Publication Date: 2025.05.15 SEIKO EPSON CORP

AI summary

A phosphor includes a phosphor body including 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 content of the phosphor phase is 56 vol % or more and 70 vol % or less in a volume ratio with respect to the phosphor body. A ratio of Ce to A in terms of number of atoms is 0.004 or more and 0.04 or less. A thickness of the phosphor body is 45 μm or more and 150 μm or less. A is at least one selected from the group consisting of Lu, Gd, Tb, Ga, and Y, and B is Al.