LED Backlight Red Color Reproducibility via Segmented Spectrum
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Solution Overview
Problem
Conventional on-vehicle liquid crystal display devices using cold cathode fluorescent lamps face issues with reliability, vibration resistance, shock sensitivity, and environmental concerns due to mercury content, and the transition to white-emitting LED backlight devices results in poor red color reproducibility.
Innovation Solution
A liquid crystal display device employing a white-emitting LED backlight with a combination of blue-emitting, red-emitting, and green-emitting phosphors, and a color filter with specific emission spectrum peaks and pigment compositions to enhance red color reproducibility, ensuring deep red chromaticity within a defined xy chromaticity coordinate system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a white-emitting LED device with blue-emitting LED and yellow phosphor is used as backlight, then energy efficiency and environmental compliance are improved, but red color reproducibility deteriorates
Solution Approach 1:
The patent segments the backlight system into multiple independent LED chips with different emission wavelengths (blue LED at 440-470nm, cyan LED at 470-495nm, green LED at 495-550nm) instead of using a single white LED. This segmentation allows each wavelength component to be independently optimized and controlled, enabling excellent red color reproduction while maintaining energy efficiency and environmental compliance.
Solution Approach 2:
The patent employs a composite backlight structure combining multiple LED light sources with different spectral characteristics. By integrating blue, cyan, and green LED chips with appropriate phosphors, the system creates a composite light source that provides both the energy efficiency of LED technology and the broad spectrum needed for excellent red color reproduction.
2Illumination intensity
If conventional cold cathode fluorescent lamp is used as backlight, then red color reproducibility is maintained, but reliability and environmental compliance deteriorate
Solution Approach 1:
The patent replaces the mechanical cold cathode fluorescent lamp system with a solid-state LED-based backlight system. This substitution eliminates the fragile glass tube and mercury-filled structure of CCFL, providing superior vibration and shock resistance while maintaining or improving color reproduction through the multi-LED configuration.
3Ease of manufacture
If white-emitting LED with blue LED and YAG phosphor is used, then manufacturing simplicity is improved, but red color emission is insufficient
Solution Approach 1:
The patent divides the backlight into multiple independent LED modules, each responsible for specific wavelength ranges. This segmentation, while slightly increasing manufacturing complexity, enables precise control over the spectral output, particularly enhancing red wavelength emission by including dedicated green LED components that phosphor-convert to red.
Solution Approach 2:
The patent changes the spectral parameters of the backlight by introducing multiple LED types with different peak wavelengths and using various phosphor materials. This parameter optimization allows the system to achieve excellent red color reproduction while maintaining reasonable manufacturing simplicity through standardized LED module designs.
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 excellent red color reproducibility and compliance with environmental regulations by using a mercury-free white-emitting LED backlight and a color filter with optimized pigment ratios, effectively addressing the limitations of previous technologies.
Implementation Method 1
a white-emitting LED device which emits a white light arising from a color mixture created through a combination of a blue-emitting LED, a red-emitting phosphor and a green-emitting phosphor
Data Source
AI summary
Disclosed a liquid crystal display device including a backlight device including a white-emitting LED device which emits a white light arising from a color mixture created through a combination of a blue-emitting LED, a red-emitting phosphor and a green-emitting phosphor, and a color filter equipping color pixels exhibiting plural colors including a red pixel and formed on a transparent substrate, wherein the white-emitting LED device is enabled to exhibit an emission spectrum having a first peak wavelength falling within a range of 440-470 nm, a second peak wavelength falling within a range of 510-550 nm and a third peak wavelength falling within a range of 630-670 nm, and a red display chromaticity of the liquid crystal display device is confined within a region bounded by lines connecting four points (0.620, 0.280), (0.620, 0.300), (0.680, 0.315) and (0.680, 0.280) based on an xy chromaticity coordinate system.