Phosphor-Converted Backlight for Wide Gamut Without Brightness Loss
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Solution Overview
Problem
Existing color image display devices face challenges in achieving high color purity and brightness due to inadequate emission from backlights, particularly with yellow-emitting phosphors, which result in reduced color reproducibility and increased brightness at the expense of NTSC ratio, and the complexity of combining red, green, and blue LEDs for improved color reproduction.
Innovation Solution
A semiconductor light emitting device with specific phosphors, including a green emitting phosphor with an emission peak in the 515-550 nm range and a red emitting phosphor with a narrow emission peak in the 610-650 nm range, combined with a blue or deep blue light source, to enhance light use efficiency and NTSC ratio without compromising brightness, allowing for broad color reproducibility and easy white balance adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If yellow-emitting phosphors are used in the backlight, then brightness is improved, but color reproducibility deteriorates
Solution Approach 1:
The patent segments the backlight system into multiple independent light emitting devices, each containing phosphors that emit light in specific wavelength regions (red, green, blue). This segmentation allows each device to contribute specialized color components to the overall backlight, improving color reproducibility while maintaining brightness through combined emission.
2Manufacturing precision
If the NTSC ratio is increased to improve color purity, then color reproduction range is improved, but brightness deteriorates
Solution Approach 1:
The patent merges multiple light emitting devices with different phosphor combinations into a single backlight system. Each device is optimized for specific color regions (red, green, blue), and their combined emission provides both high color purity (high NTSC ratio) and sufficient brightness through additive color mixing.
3Manufacturing precision
If red, green, and blue LEDs are combined to improve color reproduction, then color reproducibility is improved, but device complexity increases
Solution Approach 1:
The patent creates universal light emitting devices that can serve multiple functions: each device contains phosphors for specific color regions and can be mounted in standardized positions. These multi-functional devices simplify the overall system by replacing the need for separate red, green, and blue LED components with integrated units that perform all color functions.
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 high luminance, broad color reproducibility, and improved NTSC ratio while maintaining image brightness, simplifying the mounting process and facilitating white balance adjustment by using a single chip for red, green, and blue emissions.
Implementation Method 1
A semiconductor light emitting device with specific phosphors, including a green emitting phosphor with an emission peak in the 515-550 nm range and a red emitting phosphor with a narrow emission peak in the 610-650 nm range, combined with a blue or deep blue light source
Data Source
AI summary
To provide a semiconductor light emitting device which is capable of accomplishing a broad color reproducibility for an entire image without losing brightness of the entire image. A light source provided on a backlight for a color image display device has a semiconductor light emitting device comprising a solid light emitting device to emit light in a blue or deep blue region or in an ultraviolet region and phosphors, in combination. The phosphors comprise a green emitting phosphor and a red emitting phosphor. The green emitting phosphor and the red emitting phosphor are ones, of which the rate of change of the emission peak intensity at 100° C. to the emission intensity at 25° C., when the wavelength of the excitation light is 400 nm or 455 nm, is at most 40%.