Four-Wavelength Cold Cathode Fluorescent Lamp for LCD Backlight
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Solution Overview
Problem
Existing liquid crystal display devices using three-wavelength cold cathode fluorescent lamps struggle to achieve pure colors and a broad color reproduction range, particularly failing to accurately represent blue and green colors due to wavelength overlap and limited red color range.
Innovation Solution
A four-wavelength cold cathode fluorescent lamp is developed, utilizing a first red phosphor with a dominant wavelength of 620 nm, a second red phosphor with 658 nm, a green phosphor with 515 nm, and a blue phosphor with 447 nm, formed from specific materials like YVO4, Ge, manganese-added BAM group, and SCA group phosphors, respectively, to enhance color separation and reproduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a three-wavelength cold cathode fluorescent lamp is used, then the device structure is simple, but the color reproduction range is limited and pure colors cannot be achieved
Solution Approach 1:
The patent segments the red color emission into two separate phosphors with different dominant wavelengths (620nm and 658nm). This segmentation allows the red color band to be divided into distinct wavelength regions, preventing overlap with green and blue phosphors, thereby achieving pure colors and expanded color reproduction range while maintaining a single lamp structure
Solution Approach 2:
The patent uses composite phosphor materials including YVO4 for red (620nm), Ge for red (658nm), manganese-added BAM group for green (515nm), and SCA group for blue (447nm). These composite material selections enable precise wavelength control and prevent spectral overlap, resolving the contradiction between simple structure and color accuracy
2Illumination intensity
If phosphors with overlapping wavelengths are used, then the lamp can cover a broad spectrum, but pure colors cannot be realized due to wavelength overlap
Solution Approach 1:
The patent applies local quality by assigning specific dominant wavelengths to each phosphor type: red phosphors at 620nm and 658nm, green at 515nm, and blue at 447nm. Each phosphor is optimized for its specific wavelength region, creating localized spectral peaks that do not overlap, thereby achieving both broad spectral coverage and high color purity
Solution Approach 2:
The patent changes the key parameter of phosphor dominant wavelength to achieve non-overlapping spectral distribution. By selecting specific wavelength values (620nm, 658nm, 515nm, 447nm) and controlling the full width at half maximum (FWHM) of each phosphor, the patent prevents spectral overlap while maintaining broad coverage
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 enables the realization of pure colors and significantly expands the color reproduction range beyond 100% of the NTSC standard, allowing for clear division of color areas without overlap, thereby improving color accuracy and range.
Implementation Method 1
phosphor 8 is spread over the internal surface of the glass tube 2... the ultraviolet rays are converted into visible rays by the phosphor 8, thereby emitting light through the glass tube 2
Data Source
AI summary
This invention relates to a backlight unit of a liquid crystal display device using a cold cathode fluorescent lamp that is capable of realizing pure colors and having a broad color reproduction range. A backlight unit of a liquid crystal display device according to an embodiment of the present invention includes at least one lamp including a first red phosphor having a dominant wavelength of about 620 nm, a second red phosphor having a dominant wavelength of about 658 nm, a green phosphor having a dominant wavelength of about 515 nm and a blue phosphor having a dominant wavelength of about 447 nm; a bottom cover in which the lamp is disposed; and an optical member disposed on the lamp.