Fluorescent Sheet With Transflective Film For LCD Light Efficiency
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Solution Overview
Problem
Liquid crystal displays (LCDs) face challenges with luminance uniformity and color purity when using cold cathode fluorescent lamps (CCFLs) as backlight sources, and high costs and environmental concerns with semiconductor nanocrystals, which also have low light directionality and color reproducibility.
Innovation Solution
A fluorescent sheet using organic and inorganic phosphors with a transflective film is applied to improve light efficiency, replacing semiconductor nanocrystals and enhancing color reproducibility and purity by converting incident light into white light for LCDs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If semiconductor nanocrystals are used in the fluorescent sheet, then color purity and color reproducibility are improved, but manufacturing cost increases and environmental harm occurs
Solution Approach 1:
The patent changes the material parameters by replacing semiconductor nanocrystals with organic and inorganic phosphors that have appropriate emission characteristics. The organic phosphors include compounds like coumarin, fluorescein, and rhodamine derivatives, while inorganic phosphors include compounds like Sr2Si5N3:Eu and SrAlSiN3:Eu, which can achieve comparable color purity without the high cost and environmental issues of semiconductor nanocrystals
Solution Approach 2:
The patent employs cheaper phosphor materials (organic and inorganic compounds) that can be easily synthesized and applied, replacing expensive semiconductor nanocrystals. These phosphors can be incorporated into the fluorescent sheet at lower cost while maintaining acceptable performance, making the overall display device more economically viable
2Manufacturing precision
If semiconductor nanocrystals are used in the fluorescent sheet, then color purity is improved, but environmental harm occurs
Solution Approach 1:
The patent converts the potentially harmful semiconductor nanocrystal materials into beneficial organic and inorganic phosphor alternatives. These phosphors emit light in the desired wavelength ranges (red, green, blue) without the environmental toxicity associated with cadmium-based semiconductor nanocrystals, thus eliminating the harmful effect while preserving the beneficial color purity effect
Solution Approach 2:
The patent employs cheaper phosphor materials (organic and inorganic compounds) that can be easily synthesized and applied, replacing expensive semiconductor nanocrystals. These phosphors can be incorporated into the fluorescent sheet at lower cost while maintaining acceptable performance, making the overall display device more economically viable
3Ease of manufacture
If CCFL is used as the light source, then manufacturing cost is reduced, but luminance uniformity and color purity deteriorate
Solution Approach 1:
The patent segments the backlight unit into distinct functional components: a LED light source for cost-effectiveness, a fluorescent sheet with multiple phosphor layers for color conversion, and optical compensation films for luminance uniformity. This segmentation allows each component to be optimized independently, achieving both low cost and high luminance uniformity
Solution Approach 2:
The patent applies local quality improvements by using different phosphor materials in different regions of the fluorescent sheet. For example, red phosphors (Sr2Si5N3:Eu), green phosphors (SrAlSiN3:Eu), and blue phosphors are strategically placed to achieve uniform color distribution. Additionally, optical compensation films with specific refractive indices are applied in specific locations to correct luminance non-uniformity
4Manufacturing precision
If semiconductor nanocrystals are used, then color reproducibility is improved, but light directionality remains poor with only about 50% light directed toward the front
Solution Approach 1:
The patent addresses the light directionality issue by adding optical compensation films with microlens structures or prism patterns on the front surface of the display. These structures redirect light from multiple angles into the viewing direction, effectively converting omnidirectional emission into directional output without changing the semiconductor nanocrystal or phosphor materials themselves
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 reduces manufacturing costs, enhances light efficiency, and improves color reproducibility and purity without environmental harm, addressing the limitations of previous technologies.
Implementation Method 1
a color conversion film including fluorescent dots and a polymer layer, the fluorescent dots distributed within the polymer layer
Data Source
AI summary
A color conversion film includes fluorescent dots and a polymer layer, the fluorescent dots distributed within the polymer layer; a barrier film at one surface of the color conversion film; and a transflective film at another surface of the color conversion film. An organic or inorganic phosphor may be partially or entirely applied to the fluorescent sheet and the transflective film is applied to a bottom surface of the fluorescent sheet, thereby enhancing light efficiency without causing harm to the environment, as well as reducing a manufacturing cost.