Backlight Unit with Green Lasers and Red Phosphor for Wide Color Gamut
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Solution Overview
Problem
Conventional liquid crystal display backlight units are limited in their ability to produce a wider range of colors, particularly failing to meet the color requirements of new display standards such as BT 0.2020, which demand a broader color gamut.
Innovation Solution
A backlight unit comprising a light-guide plate, blue LEDs, green semiconductor lasers, and a red phosphor sheet, where the red phosphor material is excited by blue light to emit red light, combined with green light from the lasers, producing white light with a broader color spectrum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional blue LEDs and yellow phosphor are used for backlight, then the structure is simple and manufacturing is easy, but the color gamut is limited and cannot meet new display standards
Solution Approach 1:
The patent combines multiple light sources (blue LEDs and green semiconductor lasers) and phosphor materials (yellow and red phosphors) into a single integrated backlight unit. This merging of components enables the system to produce a broader color gamut by emitting blue, green, and red light simultaneously, while maintaining a unified structure that includes a light guide plate, diffuser sheet, and integrated light source assembly.
Solution Approach 2:
The patent uses composite phosphor materials including both yellow phosphor (Y3Al5O12:YAG) and red phosphor (CaAlSiN3) in combination with blue LEDs and green semiconductor lasers. This composite approach creates a multi-component light emission system that achieves expanded color gamut coverage, particularly for BT 2020 display standards, by combining the spectral characteristics of different materials.
2Adaptability or versatility
If multiple light sources and phosphors are combined to expand color gamut, then color rendering is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent segments the backlight unit into distinct functional modules: a light guide plate with integrated light sources (blue LEDs and green semiconductor lasers) mounted on its rear surface, a phosphor sheet containing both yellow and red phosphors positioned on the front surface, and a diffuser sheet. This segmentation allows each component to be manufactured and tested separately before final assembly, simplifying the overall manufacturing process despite the multiple components involved.
Solution Approach 2:
The light guide plate serves multiple functions simultaneously: it acts as a structural support for mounting the light sources, serves as a light distribution medium to uniformize the emitted light, and provides optical coupling between the light sources and phosphor materials. This multi-functionality reduces the need for additional separate components, thereby simplifying assembly.
3Adaptability or versatility
If red phosphor is added to blue LED system, then color gamut is expanded, but light extraction efficiency may be compromised
Solution Approach 1:
The patent applies different phosphor materials at different locations: yellow phosphor (Y3Al5O12:YAG) is positioned in proximity to the blue LEDs for efficient blue-to-yellow conversion, while red phosphor (CaAlSiN3) is positioned to receive both blue LED light and green semiconductor laser light. This localized arrangement optimizes the excitation conditions for each phosphor type, ensuring high conversion efficiency while achieving broad color gamut coverage.
Solution Approach 2:
The patent employs dynamic control of the light sources, including independent intensity modulation of blue LEDs and green semiconductor lasers, and corresponding adjustment of phosphor emission. This dynamic control allows optimization of the balance between blue, green, and red light components to maintain high overall light extraction efficiency while achieving the desired color gamut expansion for BT 2020 standards.
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
This configuration enables the production of a wider range of colors, exceeding the NTSC standard, thereby enhancing color rendering and light output while maintaining high light extraction efficiency.
Implementation Method 1
The red phosphor material is excited by light from the blue light emitting diodes and emits red light
Implementation Method 2
a plurality of green semiconductor lasers having emission peaks at green light wavelengths
Data Source
AI summary
A backlight unit includes a light-guide plate, a light source, and a phosphor sheet including a red phosphor material. The light source includes blue light emitting diodes, and green semiconductor lasers. The red phosphor material is excited by light from the blue light emitting diodes and emits red light. The phosphor sheet is solid and disposed on a surface of a first principal plane of the light-guide plate to define a first mixing light emission surface on the first principal plane of the light-guide plate from which green light emitted from the green semiconductor lasers and blue light from the blue light emitting diodes are emitted toward the phosphor sheet and a second mixing light emission surface on the phosphor sheet from which red light emitted from the red phosphor material, green light emitted from the green semiconductor lasers, and blue light from the blue light emitting diodes are emitted.