White LED Backlight for EBU Standard Color Reproducibility
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Solution Overview
Problem
Current liquid crystal display devices fail to achieve satisfactory color reproducibility conforming to the EBU standard, despite advancements in color filters, as no suitable backlight has been developed to match the required color reproduction standards.
Innovation Solution
A white LED backlight is designed with a specific emission spectrum, incorporating ultraviolet or purple light-emitting diodes and a phosphor layer comprising green, blue, and red phosphors, which emits light peaks in defined ranges to achieve the EBU standard color reproducibility, utilizing phosphors like divalent europium-activated silicate, halo-phosphate, and europium-activated oxysulfide phosphors to produce high-brightness white light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional backlights are used with color filters, then device complexity is reduced, but color reproducibility does not meet EBU standard
Solution Approach 1:
The backlight is segmented into multiple independent light sources emitting at different wavelengths (violet LED at 405-450nm, blue LED at 450-480nm, green LED at 500-550nm, yellow LED at 560-580nm, red LED at 600-650nm). Each wavelength component can be independently controlled and optimized, enabling precise spectral shaping to achieve EBU color reproduction standards while maintaining manageable device complexity through modular design
Solution Approach 2:
The patent employs composite light emission by combining multiple LED types with different emission spectra. Each LED type contributes specific wavelength ranges, and their combined output creates a composite spectrum that, when filtered through the color filter array, achieves accurate color reproduction conforming to EBU standards
2Illumination intensity
If multiple phosphors are combined in white LED, then illumination intensity increases, but emission spectrum control becomes difficult
Solution Approach 1:
Instead of using a single white LED with multiple phosphors, the patent segments the light source into multiple individual LEDs, each emitting in a specific wavelength range. This segmentation provides precise control over the emission spectrum while maintaining high illumination intensity through the combined output of all LED components
Solution Approach 2:
The patent controls the emission spectrum by adjusting parameters such as the number of LEDs, their arrangement, driving currents, and individual LED characteristics. This enables independent optimization of each wavelength component's intensity and spectral shape, achieving both high brightness and precise spectral control
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 white LED backlight enables liquid crystal display devices to achieve color reproducibility comparable to CRTs, meeting the EBU standard by adjusting the emission spectrum to match the required intensity ratios and peak wavelengths, thereby improving image quality in broadcasting and video creation applications.
Implementation Method 1
a phosphor layer comprising green, blue, and red phosphors, which emits light peaks in defined ranges
Implementation Method 2
a light-emitting element including at least one selected from an ultraviolet light-emitting diode, a purple light-emitting diode
Data Source
AI summary
In a embodiment, a white LED for a backlight of a liquid crystal display device conforming to the EBU standard includes an ultraviolet (purple) light-emitting element, and a phosphor layer which contains 1 to 10 wt % of a green phosphor including a divalent europium-activated silicate phosphor, 40 to 80 wt % of a blue phosphor including at least one selected from a divalent europium-activated halo-phosphate phosphor and a divalent europium-activated aluminate phosphor, and 10 to 50 wt % of a red phosphor including at least one selected from a europium-activated lanthanum oxysulfide phosphor and a europium-activated yttrium oxysulfide phosphor.