LED Package Refractive Index Matching for Color Stability

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Solution Overview

Problem

Light emitting diode (LED) packages experience color variation due to significant differences in refractive indices between the luminescent and encapsulant layers, leading to unwanted total reflection and altered light emission.

Innovation Solution

The implementation of a light emitting device package with a luminescent layer and an encapsulant layer where the effective refractive index of the encapsulant layer deviates by 10% or less from the luminescent layer, utilizing high-refractive particles to match the refractive indices, thereby reducing color variation and total reflection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If the encapsulant layer uses a material with a significantly different refractive index from the luminescent layer, then the light extraction efficiency may be improved through total internal reflection, but color variation increases and light emission consistency deteriorates

Engineering Contradiction:

Improvelight extraction efficiencyVSAvoidcolor consistency

Core Design Contradiction:

Use of energy by moving objectVSStability of the object's composition

Solution Approach 1:

The patent modifies the refractive index parameter of the encapsulant layer by incorporating particles with high refractive indices (such as TiO2, SiO2, or ZrO2) into the encapsulant material. This changes the effective refractive index of the encapsulant layer to be closer to that of the luminescent layer, thereby reducing color variation while maintaining adequate light extraction efficiency.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The encapsulant layer is constructed as a composite material consisting of the base encapsulant material (such as silicone or epoxy resin) combined with dispersed high-refractive-index particles. This composite structure allows the encapsulant layer to achieve an effective refractive index that is optimized for both light extraction and color consistency, resolving the contradiction between these two requirements.

Inventive Principle:

Principle #40Composite materials

2Illumination intensity

If the refractive index difference between luminescent and encapsulant layers is large, then light directionality is enhanced, but total reflection increases causing light loss

Engineering Contradiction:

Improvelight directionalityVSAvoidlight loss due to total reflection

Core Design Contradiction:

Illumination intensityVSLoss of energy

Solution Approach 1:

The patent adjusts the refractive index parameter of the encapsulant layer by adding particles with high refractive indices. This reduces the refractive index mismatch at the interface between the luminescent and encapsulant layers, thereby reducing total internal reflection and minimizing light loss while maintaining acceptable light directionality.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If standard encapsulant materials are used without refractive index matching, then manufacturing is simpler and cost is lower, but color variation and light emission consistency are poor

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidcolor uniformity

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent employs a composite encapsulant material that combines a standard encapsulant base material with dispersed high-refractive-index particles. This approach maintains the ease of manufacturing associated with standard materials while achieving the color uniformity and light emission consistency that would otherwise require complex refractive index matching, thus resolving the contradiction between manufacturing simplicity and product quality.

Inventive Principle:

Principle #40Composite materials

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 minimizes color variation and enhances light efficiency by reducing total reflection at the boundary between the luminescent and encapsulant layers, ensuring consistent light emission.

Implementation Method 1

an effective refractive index of the encapsulant layer has a deviation of 10% or less with respect to an effective refractive index of the luminescent layer

Methodology Applied

Scientific EffectRefraction: Refraction

Implementation Method 2

significant differences in refractive indices between the luminescent and encapsulant layers, leading to unwanted total reflection

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Data Source

PatentUS8791495B2Light emitting device package and lighting system

Publication Date: 2014.07.29 SUZHOU LEKIN SEMICON CO LTD

AI summary

Disclosed is a light emitting device package. The light emitting device package includes a body; first and second electrode layers on the body; a light emitting device electrically connected to the first and second electrode layers on the body; a luminescent layer on the light emitting device; and an encapsulant layer including particles on the luminescent layer, wherein an effective refractive index of the encapsulant layer has a deviation of 10% or less with respect to an effective refractive index of the luminescent layer.