White Persistent Phosphor Blend Color Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing white persistent phosphor blends composed of blue, green, and red phosphors suffer from color instability due to different decay rates and low intensity, making them unsuitable for long-lasting white color emission.
Innovation Solution
A blend of a first persistent phosphor (Ca1-y-zAl2O4:Eu2+, Nd3+) and a second persistent phosphor (Sr4-y-zAl14O25:Eu2+, Dy3+) combined with a third non-persistent phosphor excited by emissions from the persistent phosphors, achieving a stable white appearance through controlled emission spectra and decay rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a blend of blue, green, and red persistent phosphors is used to produce white persistent phosphor, then the white color emission is achieved, but the color changes with time due to different decay rates of each phosphor
Solution Approach 1:
The patent changes the parameters of the phosphor blend by selecting specific persistent phosphors with matched decay characteristics (blue persistent phosphor with 420-470 nm emission and green persistent phosphor with 460-535 nm emission) and combining them with a non-persistent phosphor. This parameter selection ensures that the persistent phosphors decay at similar rates, maintaining color stability over time while achieving long persistence.
Solution Approach 2:
The patent creates a composite phosphor material system consisting of multiple phosphor components: blue persistent phosphor (CaAl2O4:Eu2+,Nd3+), green persistent phosphor (Sr4Al14O25:Eu2+,Dy3+), and non-persistent phosphor (YAG:Ce3+). This composite structure allows the persistent phosphors to provide long-lasting emission while the non-persistent phosphor enhances initial intensity, and the specific composition ratios maintain color stability.
2Illumination intensity
If a blend of blue, green, and red persistent phosphors is used to produce white persistent phosphor, then the white color emission is achieved, but the intensity is low and persistence is short within the white color regime
Solution Approach 1:
The patent optimizes the emission wavelength parameters of the phosphors to maximize overlap and energy transfer efficiency. The blue persistent phosphor (420-470 nm) and green persistent phosphor (460-535 nm) are selected to excite the non-persistent yellow phosphor (560-650 nm emission), creating a synergistic effect that enhances overall intensity while maintaining long persistence through the persistent phosphor components.
Solution Approach 2:
The composite phosphor system combines persistent phosphors (for long duration emission) with a non-persistent phosphor (for high initial intensity). The specific combination of CaAl2O4:Eu2+,Nd3+ and Sr4Al14O25:Eu2+,Dy3+ persistent phosphors with YAG:Ce3+ non-persistent phosphor creates a material that exhibits both high initial intensity and long persistence times exceeding 2 hours.
3Ease of manufacture
If conventional phosphor blends are used, then simple formulation is achieved, but color stability and intensity are insufficient for long-lasting white emission
Solution Approach 1:
The patent specifies precise compositional parameters and ratios for the phosphor blend to achieve optimal performance. The blue persistent phosphor contains Eu2+ (0.005-0.05 mol) and Nd3+ (0.01-0.05 mol), the green persistent phosphor contains Eu2+ (0.005-0.05 mol) and Dy3+ (0.01-0.05 mol), and the non-persistent phosphor contains Ce3+ (0.01-0.05 mol). These parameter specifications ensure reliable color stability and high intensity while maintaining ease of manufacture through standard phosphor synthesis methods.
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 blend exhibits high initial intensity, long persistence, and color stability over time, providing a stable white color emission suitable for various applications requiring long-term light output.
Implementation Method 1
white persistent phosphor blend... a first persistent phosphor, a second persistent phosphor and a third phosphor that is excited by emissions from the persistent phosphors. Once the phosphor blend or layered structure has been excited it appears white in an absence of ambient light.
Implementation Method 2
The third phosphor is a non-persistent phosphor that is excited at a wavelength in a range of 300-500 nm, and in particular, at about 460 nm.
Data Source
AI summary
This disclosure features a blend, or use together in at least two layers of an article of manufacture, of a first persistent phosphor, a second persistent phosphor and a third phosphor. The first persistent phosphor has a formula I:Cax-y-z-aAaAl2-m-n-o-pOd:Euy,REz,Bm,Znn,Coo,Scp Iwhere the variables are defined in the disclosure. The second persistent phosphor has a formula II:Srx-y-z-aAaAl14-m-n-o-pOd:Euy,REz,Bm,Znn,Coo,Scp IIwhere the variables are defined in the disclosure. The third phosphor is a non-persistent phosphor that is excited at a wavelength in a range of 300-500 nm. Also featured is an article of manufacture including the blend or the phosphors present in at least two layers. Once the blend or layered structure comprising the three phosphors has been excited it can appear white in an absence of ambient light.