LED Backlight Spectral Control for Wide Color Gamut LCDs
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional color liquid crystal display (LCD) apparatuses using CCFL backlights have limited color purity and gamut, failing to meet the NTSC color reproducing range, and pose environmental concerns due to mercury content.
Innovation Solution
A backlight device comprising red, green, and blue light emitting diodes with specific half-value width ranges and chromaticity points is used to generate white light, improving color purity and broadening the color gamut to achieve a color reproducing range of at least 100% NTSC.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If CCFL is used as the backlight light source, then the display apparatus can be manufactured with conventional technology, but the color reproducing range is narrower than the NTSC standard and color purity is poor
Solution Approach 1:
The patent changes the spectral parameters of the light source by using LEDs with specific peak wavelengths (red: 610-680nm, green: 500-560nm, blue: 430-480nm) and controlled half-value widths. This parameter optimization enables the color reproducing range to reach 100% NTSC or more while maintaining manufacturability through standard LED technology.
Solution Approach 2:
The patent employs a composite light source system combining three different wavelength LEDs (red, green, blue) to create a broadband spectrum that covers the visible range. This composite approach synthesizes a light source with superior color rendering properties compared to single-source CCFL, achieving broad color gamut while remaining manufacturable.
2Ease of manufacture
If CCFL is used as the backlight light source, then the display can be produced with existing technology, but the color purity is poor and the color reproducing range does not meet NTSC standards
Solution Approach 1:
The patent optimizes the spectral parameters of individual LEDs, specifically controlling the half-value width to be 30-50nm for green LEDs and 20-40nm for red and blue LEDs. This parameter control ensures narrow spectral bands that prevent color mixing, thereby achieving high color purity and 100% NTSC or more color reproducing range while using manufacturable LED technology.
3Illumination intensity
If LEDs with broad spectrum are used to increase luminance, then the brightness is improved, but the color purity decreases and color reproducing range narrows
Solution Approach 1:
The patent identifies and controls the half-value width parameter of LED spectra as a critical factor. By specifying narrow half-value widths (green: 30-50nm, red/blue: 20-40nm), the patent achieves a balance where sufficient luminance is obtained while maintaining narrow spectral bands that ensure high color purity and broad color reproducing range.
Solution Approach 2:
The patent applies different spectral characteristics to different color channels. Specifically, it uses narrower half-value widths for red and blue LEDs (20-40nm) compared to green LEDs (30-50nm), optimizing each color channel's spectral quality to maximize overall color purity while maintaining adequate luminance across all channels.
4Illumination intensity
If the half-value width of green LED is increased to improve luminance, then the brightness increases, but the color mixing with blue and red increases, reducing color purity
Solution Approach 1:
The patent sets specific ranges for the half-value width of green LEDs (30-50nm) that balance luminance output with spectral purity. This controlled parameter range ensures that green light provides sufficient brightness while its spectral bandwidth remains narrow enough to prevent excessive overlap with blue and red channels, thereby maintaining high color purity and broad color reproducing range.
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 enhances color purity and expands the color gamut beyond conventional CCFL limitations, ensuring a broader color reproducing range while reducing environmental impact by replacing mercury-containing CCFLs with LED technology.
Implementation Method 1
a light source, made up by a red light emitting diode emitting red light
Implementation Method 2
red light emitting diode emitting red light with a half-value width hwr
Implementation Method 3
color mixing means for mixing the red light, green light and blue light emitted by the light source to generate the white light
Data Source
AI summary
Disclosed is a backlight device used for a color liquid crystal display (LCD) apparatus. The red light, green light and blue light, generated by a light source, made up by a red light emitting diode (21R), a green light emitting diode (21G) and a blue light emitting diode (21B), respectively, are mixed together to generate white light. The red light has a half-value width hwr such that 15 nm≦hwr≦30 nm, and the green light has a half-value width hwg such that 25 nm≦hwg≦50 nm. The blue light has a half-value width hwb such that 15 nm≦hwb≦30 nm. The white light illuminates a transmissive color liquid crystal display panel (10) from its back side. The transmissive color liquid crystal display panel includes a color filter (19) made up by a tristimulus filter for wavelength-selecting and transmitting red light, green light and blue light.