Lighting Apparatus Scattering Medium for Photoluminescent Lifetime
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Solution Overview
Problem
Lighting apparatuses with photoluminescent materials face significant degradation when exposed to primary light, leading to substantial loss of absorbance and reduced lifetime, as the degradation of photoluminescent material results in a substantial decrease in the absorbance of blue primary light, limiting their operational duration.
Innovation Solution
The conversion material is adapted such that the relative decrease in concentration of the converting photoluminescent material is greater than the relative decrease in intensity of the secondary light when illuminated by blue primary light, ensuring that the absorbance of blue primary light remains only slightly reduced, even after significant degradation of the photoluminescent material, thereby extending the lifetime of the lighting apparatus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If photoluminescent material is used to convert blue primary light into secondary light, then the lighting apparatus can generate desired color light, but the photoluminescent material degrades over time when illuminated by blue primary light, leading to substantial loss of absorbance and reduced lifetime
Solution Approach 1:
The patent introduces a scattering medium as an intermediary between the blue primary light and the photoluminescent material. This scattering medium diffuses the incident blue light before it reaches the photoluminescent material, reducing the concentration of direct high-energy photons that cause degradation. The scattering medium acts as a buffer that protects the photoluminescent material while still allowing sufficient light transmission for conversion to secondary light, thereby extending the operational lifetime of the lighting apparatus.
2Use of energy by moving object
If the concentration of converting photoluminescent material is increased to maintain absorbance, then the initial light conversion efficiency improves, but the degradation rate increases, leading to faster loss of absorbance over time
Solution Approach 1:
The scattering medium serves as a protective intermediary that allows the system to use lower concentrations of photoluminescent material while maintaining effective light absorption. By diffusing the blue light, the scattering medium increases the optical path length and distributes the photon flux more evenly, reducing the peak intensity that causes degradation. This enables the system to achieve the required absorbance with less photoluminescent material, thereby slowing degradation and extending operational lifetime.
Solution Approach 2:
The patent changes the optical parameters of the system by introducing a scattering medium with specific scattering coefficients. This modifies the light distribution profile and intensity distribution within the photoluminescent material layer. By adjusting the scattering properties, the system optimizes the balance between light absorption efficiency and degradation rate, allowing for lower photoluminescent material concentration while maintaining performance and extending lifetime.
3Illumination intensity
If the photoluminescent material is exposed to high intensity blue primary light to maintain secondary light output, then the light conversion performance is maintained, but the degradation accelerates, causing substantial decrease in absorbance
Solution Approach 1:
The scattering medium acts as a protective intermediary that diffuses high-intensity blue primary light before it reaches the photoluminescent material. This reduces the peak intensity and concentrates photon flux, lowering the intensity-dependent degradation rate. The scattering medium allows the system to maintain high secondary light output by distributing the light more evenly across the photoluminescent material, preventing localized overheating and rapid degradation that would occur with direct high-intensity illumination.
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 adaptation allows the lighting apparatus to maintain its intensity and color temperature over a longer period, with minimal alteration in the color temperature and intensity of the secondary light, even after 90% degradation of the photoluminescent material, significantly increasing its operational lifetime.
Implementation Method 1
a conversion material for converting blue primary light into secondary light, wherein the conversion material comprises converting photoluminescent material
Implementation Method 2
The at least one phosphor can be arranged to absorb a portion of the primary radiation and to convert the absorbed primary radiation into secondary radiation
Data Source
Figure 1
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Figure 4~5
AI summary
The invention relates to a lighting apparatus comprising a conversion material (2) for converting primary light (4) into secondary light (5), wherein the conversion material (2) comprises converting photolummescent material (15), which degrades to non-converting photolummescent material over time when the conversion material (2) is illuminated by the primary light (4). The conversion material (2) is adapted such that, when the conversion material (2) is illuminated by the primary light (4), the relative decrease in concentration of the converting photolummescent material (15) within the conversion material (2) is larger than the relative decrease in intensity of the secondary light (5). This allows the lighting apparatus to provide an only slightly reduced absorbance of the primary light, even if a large part of the photolummescent material has been bleached, and thus a longer lifetime, with the same or a slightly reduced intensity of the secondary light.