Red Phosphor Composition for High Refresh Rate Displays
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Solution Overview
Problem
Conventional red phosphors, such as the MGF phosphor, have long persistence times, which can lead to low refresh rates in liquid crystal display applications, and are not efficiently excited by light emitting diodes emitting near-ultraviolet to visible light, limiting their use in mercury-free lighting systems.
Innovation Solution
A red phosphor composition represented by the formula (x−a)MgO.(a/2)Sc2O3.yMgF2.cCaF2.(1−b)GeO2.(b/2)Mt2O3:zMn4+, where x, y, z, a, b, and c satisfy specific ranges, and Mt is at least one element selected from Al, Ga, and In, is developed to improve light emission efficiency and reduce persistence time when excited by light with a peak wavelength from near-ultraviolet to visible light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional MGF phosphor is used, then red light emission is achieved, but persistence time is long which reduces refresh rate
Solution Approach 1:
The patent modifies the chemical composition parameters of the phosphor by incorporating Sc2O3 and CaF2 into the MGF phosphor structure. This compositional parameter change fundamentally alters the persistence characteristics, reducing persistence time from the conventional long duration to a shorter duration that enables high refresh rates while maintaining red light emission capability
Solution Approach 2:
The invention creates a composite phosphor material by combining MGF phosphor with Sc2O3 and CaF2 components. This composite structure integrates the red light emission property of MGF phosphor with the short persistence characteristics introduced by the Sc2O3 and CaF2 additives, achieving both color purity and fast response required for display applications
2Use of energy by moving object
If MGF phosphor is used, then manufacturing is relatively easy, but excitation efficiency with LED (near-ultraviolet to visible light) is insufficient
Solution Approach 1:
The patent adjusts the excitation wavelength parameter matching by modifying the phosphor's absorption characteristics through Sc2O3 and CaF2 incorporation. This enables the phosphor to efficiently absorb near-ultraviolet to visible light from LED sources, improving excitation efficiency while maintaining the relatively simple calcination manufacturing process at about 1200°C
3Illumination intensity
If red phosphor with narrow half-value width is used for display application, then color purity is improved, but persistence time must be short for high refresh rate
Solution Approach 1:
The patent simultaneously optimizes two critical parameters: the emission spectrum shape (half-value width) through compositional design to achieve narrow bandwidth and high color purity, and the persistence time through Sc2O3 and CaF2 incorporation to achieve short duration. This dual parameter optimization enables the phosphor to meet both color reproduction and refresh rate requirements for display applications
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 new red phosphor exhibits improved light intensity and shorter persistence times, making it suitable for high-speed liquid crystal display applications and efficient operation with light emitting diodes, while maintaining the fundamental characteristics of conventional MGF phosphors.
Implementation Method 1
a phosphor that can be excited by light having a peak wavelength in the range from near-ultraviolet light to visible light and can efficiently emit red light
Data Source
AI summary
A red phosphor including the composition represented by the following general formula.(x−a)MgO.(a/2)Sc2O3.yMgF2.cCaF2.(1−b)GeO2.(b/2)Mt2O3:zMn4+where x, y, z, a, b, and c satisfy 2.0≤x≤4.0, 0<y<1.5, 0<z<0.05, 0≤a<0.5, 0<b<0.5, 0≤c<1.5, and y+c<1.5, and Mt is at least one element selected from the group consisting of Al, Ga, and In.