Wavelength Conversion Member Refractive Index Gradient

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Solution Overview

Problem

The wavelength conversion member in existing light-emitting devices experiences reduced light extraction efficiency due to light reflection at interfaces between the phosphor layer and microspheres, limiting luminous efficiency improvement.

Innovation Solution

A wavelength conversion member is designed with a phosphor layer containing a glass matrix and inorganic phosphor powder, a glass layer with a refractive index equal to or smaller than the phosphor powder, and a microscopically uneven layer with a refractive index equal to or smaller than the glass layer, reducing light reflection and enhancing light extraction efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If a phosphor layer with high inorganic phosphor powder content is used to improve luminous efficiency, then the luminous efficiency increases, but light reflection at interfaces increases due to high refractive index, reducing light extraction efficiency

Engineering Contradiction:

Improveluminous efficiencyVSAvoidlight reflection at interfaces

Core Design Contradiction:

Loss of energyVSObject-generated harmful factors

Solution Approach 1:

The patent introduces a glass layer with intermediate refractive index between the phosphor layer (high refractive index) and the microscopically uneven layer (low refractive index). This intermediary layer acts as a refractive index bridge, gradually transitioning the optical properties and reducing light reflection at interfaces, thereby improving light extraction efficiency while maintaining high luminous efficiency

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent systematically varies the refractive index parameter across different layers by selecting appropriate glass materials and compositions. The glass layer's refractive index is specifically chosen to be between that of the phosphor layer and the microscopically uneven layer, creating a gradient that minimizes optical impedance mismatch and reduces reflection losses

Inventive Principle:

Principle #35Parameter changes

2Productivity

If a glass layer is added to reduce light reflection, then light extraction efficiency increases, but device complexity increases

Engineering Contradiction:

Improvelight extraction efficiencyVSAvoidnumber of layers

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The glass layer serves multiple functions simultaneously: it acts as an optical intermediary to reduce reflection, provides mechanical support and structural stability, and serves as a bonding interface between the phosphor layer and the microscopically uneven layer. By consolidating these functions into a single layer, the patent minimizes the increase in device complexity while achieving the desired light extraction efficiency improvement

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 described structure increases light extraction efficiency, thereby improving luminous efficiency, especially when the inorganic phosphor powder content is high, by minimizing light reflection at interfaces and maintaining mechanical strength and thermal stability.

Implementation Method 1

a glass layer disposed on a surface of the phosphor layer and having a refractive index equal to or smaller than a refractive index of the inorganic phosphor powder; and a microscopically uneven layer disposed on a surface of the glass layer and having a refractive index equal to or smaller than the refractive index of the glass layer

Methodology Applied

Scientific EffectRefraction: Refraction

Implementation Method 2

an antireflection function layer formed of the glass layer and the microscopically uneven layer is formed on the surface of the phosphor layer

Methodology Applied

Scientific EffectAntireflection function: Anti-Reflective Coating

Implementation Method 3

a phosphor layer containing a glass matrix and inorganic phosphor powder dispersed in the glass matrix; a light source for emitting ultraviolet light and a wavelength conversion member (a phosphor layer) for converting the ultraviolet light from the light source to visible light

Methodology Applied

Scientific EffectPhosphorescence: Phosphorescence

Data Source

PatentUS10580944B2Wavelength conversion member, light-emitting device, and method for manufacturing wavelength conversion member

Publication Date: 2020.03.03 NIPPON ELECTRIC GLASS CO LTD

AI summary

Provided is a wavelength conversion member that can increase the light extraction efficiency to improve the luminous efficiency. A wavelength conversion member 10 includes: a phosphor layer 1 containing a glass matrix and inorganic phosphor powder dispersed in the glass matrix; a glass layer 2 disposed on a surface of the phosphor layer 1 and having a refractive index equal to or smaller than a refractive index of the inorganic phosphor powder; and a microscopically uneven layer 3 disposed on a surface of the glass layer 2 and having a refractive index equal to or smaller than the refractive index of the glass layer 2.