LED Backlight Phosphor Mixing for NTSC and Brightness
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Solution Overview
Problem
Conventional LED backlight sources struggle to achieve both high NTSC color effect and brightness performance, often requiring adjustments that either compromise on color gamut or increase manufacturing costs and power consumption, while existing phosphor compositions limit luminous efficacy and NTSC effect.
Innovation Solution
An LED structure comprising a blue light LED chip, a red phosphor with a chemical formula of T2XF6:Mn4+, and a yellow phosphor made of (Sr,Ba,Ca)2SiO4:Eu, where the red phosphor absorbs blue light to emit red light with a wavelength of 630 nm and the yellow phosphor emits yellow light with a wavelength between 540 nm-550 nm, controlled in a mixing ratio of (2.33−1) with the red phosphor, to produce a white light within specific CIE 1931 chromaticity coordinates, enhancing NTSC effect and luminous efficacy without increasing blue LED chip size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional yellow phosphor (emission wavelength 540-570 nm) and red phosphor (emission wavelength >650 nm) are used to improve NTSC effect, then color gamut improves, but overall brightness drops and luminous efficacy decreases
Solution Approach 1:
The patent changes the emission wavelength parameter of the yellow phosphor from the conventional 540-570 nm range to a shorter wavelength range of 520-540 nm. This parameter change allows the yellow phosphor to emit light that complements the red phosphor (650-680 nm) and blue LED (430-470 nm) more effectively, achieving NTSC effect greater than 80% while maintaining high brightness and luminous efficacy greater than 70% of the standard 120 lm/W
Solution Approach 2:
The patent uses a composite phosphor system combining specifically selected yellow phosphor (emission wavelength 520-540 nm) and red phosphor (emission wavelength 650-680 nm) with a blue LED chip. This composite material approach creates a white light source where the spectral power distribution is optimized by the complementary emission characteristics of the phosphors, achieving both high NTSC effect and high luminous efficacy simultaneously
2Illumination intensity
If blue LED chip size is increased to improve brightness, then luminous flux increases, but manufacturing cost and power consumption increase
Solution Approach 1:
The patent changes the emission wavelength parameter of the yellow phosphor to 520-540 nm, which has higher luminous efficiency and better spectral matching with the red and blue components. This allows achieving the same brightness level with smaller blue LED chips, reducing manufacturing cost and power consumption while maintaining high NTSC effect
Solution Approach 2:
The patent uses phosphor down-conversion to convert blue LED light into yellow and red wavelengths, creating a complete spectrum white light. This approach is more efficient than using larger blue LEDs because the phosphors convert a portion of the blue light into the required spectral components, achieving better overall luminous efficacy
3Productivity
If yellow phosphor emission wavelength is extended beyond 540 nm to improve brightness, then luminous flux increases, but NTSC effect decreases below 80%
Solution Approach 1:
The patent sets the yellow phosphor emission wavelength parameter to 520-540 nm, which is shorter than conventional yellow phosphors. This parameter optimization ensures that the yellow phosphor emission does not encroach on the red wavelength region, allowing the red phosphor (650-680 nm) to provide sufficient red content for NTSC effect greater than 80% while the yellow phosphor contributes adequately to luminous flux
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 NTSC effect over 80% and luminous efficacy over 80% lm/W, maintaining high brightness and improving color gamut, while reducing manufacturing costs and power consumption, and ensuring compliance with the D65 white light standard.
Implementation Method 1
a red phosphor, a red phosphor that absorbs a blue light emitted from the blue light LED chip to emit a red light
Implementation Method 2
a yellow phosphor, that absorbs a blue light emitted from the blue light LED chip to emit a yellow light
Implementation Method 3
a blue light LED chip, mounted onto the base
Data Source
AI summary
An LED structure is applied to a backlight source to set a white light of a backlight module at a standard D65 position of the CIE1931 chromaticity coordinates and used together with a display module. A red phosphor for emitting a red light, a yellow phosphor for emitting a yellow light, and a blue light LED chip are provided. The mixing ratio of the red phosphor to the yellow phosphor is controlled within a range of (2.33−1):1, so that the original LED white light falls within a region enclosed by ccy≦1.8*ccx−0.12, ccy≧1.8*ccx−0.336, ccy≦0.33 and ccy≧0.15 of the CIE1931 coordinates. Since the red phosphor does not absorb or convert yellow light, the brightness loss of the yellow light that excites the yellow phosphor is minimized. A color filter may be installed to achieve better NTSC effect and luminous efficacy.