Nitride Phosphor for White LED Color Rendering

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Solution Overview

Problem

Current white LED light-emitting apparatuses face challenges in enhancing the red light component while maintaining a high green light component, which affects color rendering properties and color reproduction range.

Innovation Solution

A phosphor compound represented by the general formula MxCeyPrzSi6N8+w, where M is at least one element from La, Y, and Lu, with specific stoichiometric ratios, is developed to absorb ultraviolet to blue light and emit light with peaks in the 515-545 nm and 610-620 nm ranges, increasing the red light component and improving color rendering.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If conventional yellow phosphors are used in white LED light-emitting apparatuses, then the green light component can be maintained, but the red light component is insufficient

Engineering Contradiction:

Improvered light componentVSAvoidcolor rendering property

Core Design Contradiction:

Illumination intensityVSAdaptability or versatility

Solution Approach 1:

The patent uses a composite phosphor material containing both Ce and Pr elements in a specific ratio within a nitride host structure. This composite approach allows simultaneous achievement of green light emission (from Ce) and red light emission (from Pr), resolving the contradiction between maintaining green component and enhancing red component for improved color rendering

Inventive Principle:

Principle #40Composite materials

2Adaptability or versatility

If the phosphor emits light with peak wavelength optimized for color rendering, then the color reproduction range improves, but the energy conversion efficiency decreases

Engineering Contradiction:

Improvecolor reproduction rangeVSAvoidenergy conversion efficiency

Core Design Contradiction:

Adaptability or versatilityVSUse of energy by moving object

Solution Approach 1:

The patent creates localized emission characteristics within the phosphor structure by incorporating specific rare earth elements (Ce and Pr) at controlled concentrations. This local quality approach allows the phosphor to maintain high energy conversion efficiency at specific wavelength peaks while still providing broad color reproduction coverage through the combination of green and red emissions

Inventive Principle:

Principle #3Local quality

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 phosphor effectively increases the red light component, enhancing the color rendering property and color reproduction range of white LED light-emitting apparatuses by optimizing the light emission intensity ratio and crystal phase content.

Implementation Method 1

The phosphor absorbs light in a range from ultraviolet to blue light and emits light different from the absorbed light

Methodology Applied

Scientific EffectPhotoluminescence: Photoluminescence

Data Source

PatentUS10032965B2Phosphor, light-emitting apparatus including the same, and phosphor production method

Publication Date: 2018.07.24 NICHIA CORP

AI summary

A phosphor, which is represented by the general formula containing M, Ce, Pr, Si, and N, is provided. M is at least one element selected from the group consisting of La, Y, Tb and Lu. A molar ratio of M is greater than 2.0 and smaller than 3.5. A molar ratio of Ce is greater than 0 and smaller than 1.0. A molar ratio of Pr is greater than 0 and smaller than 0.05. A molar ratio of N is greater than 10 and smaller than 12, under the condition that a molar ratio of Si is set to 6. The phosphor further contains 10 to 10,000 ppm of fluorine.