Phosphor Emission Color Stability for Extended Light-Emitting Device Life
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Solution Overview
Problem
Conventional ultraviolet excitation type phosphors fail to maintain luminance effectively beyond 3000 hours of continuous operation, necessitating improved luminance maintenance factors for extended usage in light-emitting devices.
Innovation Solution
A phosphor with emission colors represented by xy coordinates showing a difference of 0.020 or less between maximum and minimum x and y values when excited across a range of 100 to 500 nm, ensuring stable crystal structure and reduced defects, is developed and used in light-emitting devices, along with a production method that evaluates phosphor properties across this wavelength range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional phosphors are used in light-emitting devices, then initial luminance performance is achieved, but luminance maintenance factor deteriorates after 3000 hours of continuous operation
Solution Approach 1:
The patent applies parameter changes by strictly controlling the emission color coordinates (x, y) to differ by 0.020 or less across the ultraviolet wavelength range of 100-500 nm. This parameter control ensures that the phosphor maintains consistent luminescence properties under different excitation wavelengths, thereby improving luminance maintenance factor and extending service life to 3000 hours or more.
2Illumination intensity
If phosphor composition is optimized for high emission intensity, then initial luminance is improved, but long-term luminance stability deteriorates
Solution Approach 1:
The patent changes the critical parameter from mere emission intensity to emission color consistency. By controlling the xy coordinates to vary by 0.020 or less across 100-500 nm excitation wavelengths, the invention achieves both high emission intensity and long-term luminance stability, resolving the contradiction between initial performance and long-term stability.
3Reliability
If conventional phosphor selection criteria are used, then manufacturing simplicity is maintained, but product quality and reliability deteriorate
Solution Approach 1:
The patent introduces specific parameter thresholds (xy coordinate difference ≤ 0.020 across 100-500 nm) as clear selection criteria. This transforms the manufacturing process from subjective evaluation to objective parameter-based selection, improving product reliability while maintaining manufacturing feasibility through standardized testing procedures.
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 solution achieves an excellent luminance maintenance factor, extending the service life of light-emitting devices to 3000 hours or more, with improved reliability and reduced degradation, by selecting phosphors with minimal variation in emission colors across the specified wavelength range.
Implementation Method 1
The phosphor is made to emit light by ultraviolet rays having various wavelengths
Data Source
AI summary
When a phosphor for ultraviolet excitation or visible light excitation is excited by light having wavelengths in a range of 100 to 500 nm and emission colors of the phosphor are represented by xy coordinates, the phosphor has a difference between a maximum value and a minimum value of x coordinates and a difference between a maximum value and a minimum value of y coordinates which are respectively 0.020 or less. A light-emitting device includes a light-emitting part which contains at least such a phosphor. The light-emitting part emits visible light when irradiated with ultraviolet or visible light emitted from an excitation source.