White LED Phosphor Layer Chromaticity Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
White LEDs using ultraviolet-light emitting diodes experience significant chromaticity changes due to temperature rises, which complicates their application as backlight sources in liquid crystal display devices, especially in devices exposed to high temperatures.
Innovation Solution
A white LED design featuring a phosphor layer divided into two layers, where the first layer near the light emitting element contains minimal blue phosphor and the second layer farther away contains minimal other phosphors, effectively reducing blue light absorption and maintaining chromaticity stability as temperature increases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a phosphor layer containing blue, green, and red phosphors is used with an ultraviolet-light emitting diode, then color reproducibility is wide and predetermined chromaticity is easier to obtain, but chromaticity changes significantly when temperature rises
Solution Approach 1:
The phosphor layer is divided into two distinct layers: a first phosphor layer containing blue and green phosphors closer to the ultraviolet-light emitting diode, and a second phosphor layer containing red phosphor farther away. This segmentation prevents excessive absorption of ultraviolet light by red phosphor, thereby suppressing chromaticity changes when temperature rises while maintaining wide color reproducibility
Solution Approach 2:
The invention introduces a spatial dimension (distance from the light emitting element) to control phosphor distribution. By arranging phosphors at different distances from the ultraviolet-light emitting diode, the patent optimizes the balance between color reproducibility and chromaticity stability, allowing each phosphor type to be positioned where it can effectively convert ultraviolet light without excessive absorption losses
2Illumination intensity
If blue phosphor content is increased to improve blue light emission, then blue light output increases, but chromaticity becomes more sensitive to temperature changes
Solution Approach 1:
The invention applies local quality by concentrating blue phosphor in the first phosphor layer closer to the ultraviolet-light emitting diode, while placing red phosphor in the second layer farther away. This localized distribution ensures adequate blue light output while preventing the cumulative absorption effect that causes chromaticity instability at elevated temperatures
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 significantly suppresses chromaticity changes in white LEDs, ensuring consistent performance even under elevated temperatures, making them suitable for various liquid crystal display devices.
Implementation Method 1
a phosphor layer (40) covering the transparent resin layer (30), wherein the phosphor layer (40) contains three or more types of phosphors including a blue phosphor (B), a green phosphor (G), and a red phosphor (R)
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A white LED 1 includes a light emitting element 20 with a light emission peak wavelength equal to or longer than 380 nm and equal to or shorter than 420 nm, and a phosphor layer 40 containing three or more types of phosphors including at least a blue phosphor B, a green phosphor G, and a red phosphor R and disposed in a manner to cover at least part of the light emitting element 20. The phosphor layer 40 has a first phosphor layer 41 and a second phosphor layer 42 disposed in an opposite side of a side of the light emitting element 20 of the first phosphor layer 41. In the first phosphor layer 41, a content of the blue phosphor B in an entire phosphor contained in the first phosphor layer 41 is equal to or less than 5 mass%, or the blue phosphor B is not contained. In the second phosphor layer 42, a content of phosphor other than the blue phosphor B in an entire phosphor contained in the second phosphor layer 42 is equal to or less than 5 mass%, or no phosphor other than the blue phosphor B is contained.