UV LED White Light Source Phosphor Dispersion Control
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Solution Overview
Problem
Conventional white light sources using LEDs suffer from poor light distribution and color unevenness due to the difficulty in adjusting the dispersion state of phosphors, which affects the color reproducibility and intensity of the emitted light.
Innovation Solution
A white light source comprising an ultraviolet LED chip with a phosphor layer containing red, green, and blue phosphors dispersed in a cured transparent resin, where the phosphors are optimized in terms of composition and dispersion to achieve a specific t/L ratio, ensuring effective light distribution and reduced color unevenness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If three kinds of phosphors (blue, green, and red) are mixed in the phosphor layer to improve color reproducibility, then color reproducibility is improved, but it becomes difficult to adjust the dispersion state of phosphors and light distribution deteriorates
Solution Approach 1:
The patent applies parameter changes by establishing a specific quantitative relationship between the phosphor layer thickness t and the mean free path L of phosphor particles, defined by the ratio t/L where 0.3 ≤ t/L < 1.0. This parameter control optimizes both the dispersion state of multiple phosphors and the light distribution, resolving the contradiction between color reproducibility and light distribution uniformity
Solution Approach 2:
The patent applies local quality by controlling the phosphor layer thickness to be non-uniform, with the thickness varying in the radial direction from the LED chip. Specifically, the phosphor layer thickness is smaller near the center and larger at the periphery, which compensates for the different light paths and achieves uniform light distribution while maintaining good color reproducibility
2Illumination intensity
If the phosphor layer is made thinner to improve light distribution, then light distribution improves, but color reproducibility deteriorates
Solution Approach 1:
The patent simultaneously controls two parameters: the thickness-to-mean-free-path ratio t/L and the absolute thickness distribution. By maintaining t/L within 0.3 to 1.0 while implementing a specific thickness profile (thinner at center, thicker at periphery), the patent achieves both improved light distribution and maintained color reproducibility
3Illumination intensity
If a reflector is used to stabilize light emitting direction and improve light distribution, then light distribution improves, but device complexity increases
Solution Approach 1:
The patent extracts and removes the reflector component from the LED structure, replacing it with an optimized phosphor layer configuration. By controlling the phosphor layer thickness and phosphor particle distribution, the patent achieves light distribution improvement without the added complexity of a reflector structure
Solution Approach 2:
The patent uses parameter optimization of the phosphor layer (thickness ratio t/L and thickness distribution) to achieve the light distribution function that would otherwise require a reflector, thereby simplifying the overall device structure while maintaining performance
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 optimized white light source achieves improved light distribution and reduced color unevenness, enhancing the performance of backlights, liquid crystal display apparatuses, and illuminating apparatuses by providing a more uniform and stable light emission.
Implementation Method 1
a light-emitting diode chip which is provided on the insulating substrate and emits ultraviolet light with a wavelength of 330 nm to 410 nm
Implementation Method 2
a phosphor layer which is formed so as to cover the light-emitting diode chip, contains a red emitting phosphor, a green emitting phosphor, and a blue emitting phosphor as a phosphor
Data Source
AI summary
A white light source includes: an insulating substrate; a light-emitting diode chip provided on the insulating substrate and that emits ultraviolet light with a wavelength of 330 nm to 410 nm; and a phosphor layer formed to cover the light-emitting diode chip, including a red emitting phosphor, a green emitting phosphor, and a blue emitting phosphor as a phosphor, and the phosphors are dispersed in a cured transparent resin, wherein when it is assumed that the shortest distance between a surface of the phosphor layer and a peripheral portion of the light-emitting diode chip is t(mm) and the mean free path defined by the following expression (1) is L(mm), the t and L satisfy 3.2≦t/L.[Expression 1]L=1/(n×σ) (1)(n: number of phosphors per unit volume of the phosphor layer (pcs/mm3), and σ: average cross section area of a phosphor in the phosphor layer (mm2)).