Nitride Phosphor Infrared Absorption Brightness Stability

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Solution Overview

Problem

LSN phosphors used in LEDs face issues with brightness reduction and reliability under high-output conditions, leading to changes in emission chromaticity over time, making them unsuitable for long-term use in LED packages.

Innovation Solution

A nitride phosphor with specific infrared absorption peaks and chemical composition, treated using a unique method involving a low-oxygen atmosphere and heat processing, to enhance brightness and stability, is developed. The phosphor has multiple absorption points in the infrared spectrum and a tetragonal crystal structure, with a chemical composition represented by Formulas (1) and (2), ensuring high reliability and minimal chromaticity change.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If LSN phosphors are used to improve emission brightness, then brightness is enhanced, but reliability deteriorates due to brightness reduction and chromaticity change over time under high-output conditions

Engineering Contradiction:

Improveemission brightnessVSAvoidlong-term stability

Core Design Contradiction:

Illumination intensityVSReliability

Solution Approach 1:

The patent applies parameter changes by precisely controlling the heating temperature (50-300°C), humidity (60-100% RH), and treatment time (1-100 hours) during the post-firing heating process. These parameter optimizations transform the phosphor surface properties to achieve both high brightness and long-term reliability, resolving the contradiction between emission intensity and temporal stability

Inventive Principle:

Principle #35Parameter changes

2Illumination intensity

If LSN phosphors are treated under high-humidity conditions to improve brightness, then emission intensity increases, but reliability deteriorates due to brightness degradation over time

Engineering Contradiction:

Improveemission intensityVSAvoidbrightness stability

Core Design Contradiction:

Illumination intensityVSReliability

Solution Approach 1:

The patent applies preliminary action by performing a controlled heating treatment in a high-humidity environment (60-100% RH) at 50-300°C for 1-100 hours after the main firing process. This preliminary surface treatment optimizes the phosphor's emission properties before the phosphor is encapsulated in the LED package, ensuring both high initial brightness and long-term stability against further degradation

Inventive Principle:

Principle #10Preliminary action

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 nitride phosphor exhibits high emission brightness and reliability with minimal brightness reduction and chromaticity change over time, suitable for long-term use in LED packages, outperforming conventional LSN phosphors.

Implementation Method 1

having two or more maximum absorption points in a range of 3,200 to 3,300 cm−1 in an infrared absorption (FT-IR) spectrum

Methodology Applied

Scientific EffectInfrared absorption: Absorption (EM radiation)

Data Source

PatentUS11279875B2Nitride phosphor and method for producing nitride phosphor

Publication Date: 2022.03.22 MITSUBISHI CHEM CORP

AI summary

Provided is a nitride phosphor having two or more maximum absorption points in a range of 3,200 to 3,300 cm−1 in an infrared absorption (FT-IR) spectrum. The nitride phosphor of the present invention has excellent emission characteristics and is highly reliable when used in devices.