Backlight Unit Light Conversion Layer Color Purity
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Solution Overview
Problem
Liquid crystal display (LCD) devices face challenges in achieving uniform luminance and color purity, particularly as screen size increases, with traditional cold cathode fluorescent lamps (CCFL) and white LEDs offering compromised performance in terms of cost and color reproducibility compared to three-color LED backlight units.
Innovation Solution
A backlight unit for LCDs utilizing a light emitting diode (LED) source with a light conversion layer comprising semiconductor nanocrystals and a polymer matrix, including thiol groups and unsaturated carbon-carbon bonds, to convert LED light into white light, improving color reproducibility and purity while maintaining cost competitiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If three color LEDs are used as light source, then color purity and color reproducibility are improved, but manufacturing cost increases
Solution Approach 1:
The patent uses a composite light conversion layer containing both yellow phosphor (Y3Al5O12:Ce) and red phosphor (CaAlSiN3:Eu) materials embedded in a polymer matrix. This composite approach converts blue LED light into a spectrum that achieves color purity comparable to three-color LED systems while maintaining the cost advantage of single-color LED sources.
Solution Approach 2:
The patent optimizes the weight ratio of yellow phosphor to red phosphor (specifically 95:5 to 98:2) and controls the particle size distribution of phosphor materials. These parameter changes enable precise control over the emitted light spectrum, achieving high color purity without requiring expensive three-color LED assemblies.
2Ease of manufacture
If white LED is used as light source, then manufacturing cost is reduced, but color purity and color reproducibility deteriorate
Solution Approach 1:
The patent applies local quality enhancement by strategically placing red phosphor particles (CaAlSiN3:Eu) throughout the polymer matrix to supplement the yellow phosphor emission. This localized addition of specific phosphor materials at controlled concentrations (0.1-5 wt% red phosphor in the total phosphor mixture) targets the spectral gaps in white LED output, improving color purity while maintaining cost effectiveness.
3Manufacturing precision
If semiconductor nanocrystals are used in light conversion layer, then color purity is improved, but stability and durability deteriorate due to degradation over time
Solution Approach 1:
The patent employs conventional inorganic phosphor materials (Y3Al5O12:Ce and CaAlSiN3:Eu) that, while having shorter operational lifetimes compared to ideal stable materials, provide sufficient durability for commercial applications. These phosphors are encapsulated in a protective polymer matrix that slows degradation, offering a practical balance between initial color purity performance and operational stability at reasonable cost.
Solution Approach 2:
The patent creates a composite structure where phosphor particles are embedded in a polymer matrix, providing both the desired optical properties and protective encapsulation. This composite approach shields the phosphor materials from environmental degradation factors while maintaining their light conversion efficiency, thereby improving long-term stability without sacrificing color purity.
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 provides enhanced color reproducibility and purity, maintaining luminous efficiency over time by stabilizing the semiconductor nanocrystals within a dense polymer matrix, thus improving the overall performance of LCDs without the high cost of three-color LED systems.
Implementation Method 1
a light conversion layer disposed separate from the LED light source to convert light emitted from the LED light source to white light
Data Source
AI summary
A backlight unit for a liquid crystal display device, the backlight unit including: an light emitting diode (“LED”) light source; a light conversion layer disposed separate from the LED light source to convert light emitted from the LED light source to white light and to provide the white light to the liquid crystal panel; and a light guide panel disposed between the LED light source and the light conversion layer, wherein the light conversion layer includes a semiconductor nanocrystal and a polymer matrix, and wherein the polymer matrix includes a first polymerized polymer of a first monomer including at least two thiol (—SH) groups, each located at a terminal end of the first monomer, and a second monomer including at least two unsaturated carbon-carbon bonds, each located at a terminal end of the second monomer.