Wavelength Conversion Member for White Light Emitting Devices
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Solution Overview
Problem
Existing white light emitting devices face challenges in achieving color uniformity and increasing chromaticity range due to the saturation of fluorescent output and orientation distribution of phosphor particles under high-power laser irradiation, leading to color irregularity in the output light.
Innovation Solution
A wavelength conversion member with a substrate having reflectivity and a phosphor layer featuring concave parts that scatter laser light, converting it into isotropically distributed fluorescence, enhancing absorption and emission uniformity while increasing chromaticity range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If laser light with high power density is used to improve light output, then the light output increases, but the saturation of fluorescent output occurs and conversion efficiency decreases
Solution Approach 1:
The phosphor layer is divided into multiple layers with different phosphor materials, each layer converting laser light to different wavelength ranges. This segmentation allows progressive wavelength conversion and reduces saturation in each individual layer, maintaining higher overall conversion efficiency while achieving high light output.
Solution Approach 2:
The invention transitions from a single-layer phosphor structure to a multi-layer phosphor structure, adding the dimensional aspect of layering. This enables the system to handle high power density laser light more effectively by distributing the conversion process across multiple layers, preventing saturation and maintaining efficiency.
2Power
If high power density laser light is used to improve light output, then the light output increases, but color irregularity occurs and color uniformity decreases
Solution Approach 1:
The phosphor layer is segmented into multiple layers, each containing phosphor particles with specific size distributions and wavelength conversion characteristics. This segmentation ensures uniform light output and consistent color properties across the entire irradiation area, even under high power density conditions.
Solution Approach 2:
Different regions of the phosphor layer have locally optimized properties, with each layer containing phosphor particles sized and distributed to achieve uniform excitation and emission. This local quality control ensures consistent color uniformity across the entire output area.
3Manufacturing precision
If a coating layer with concavo-convex shape is provided on phosphor particles to scatter excitation light, then color unevenness is improved, but the absorption ratio of excitation light by phosphor particles decreases and chromaticity range is reduced
Solution Approach 1:
Instead of coating all phosphor particles with a concavo-convex structure, the invention segments the approach by creating a specific layer structure where only certain layers contain phosphor particles with surface irregularities. This maintains scattering benefits while preserving absorption efficiency in other layers.
Solution Approach 2:
The concavo-convex surface structure is applied locally to specific phosphor particles in specific layers rather than universally to all particles. This local application optimizes the balance between light scattering for uniformity and absorption efficiency for chromaticity range.
4Power
If phosphor particles are irradiated with high power density laser light, then light output increases, but heat generation increases and phosphor inactivation occurs
Solution Approach 1:
The phosphor conversion process is segmented into multiple layers, which distributes the heat generation across different spatial zones. This segmentation prevents localized overheating and phosphor inactivation, allowing sustained high power density operation without degradation.
Solution Approach 2:
The multi-layer phosphor structure acts as an intermediary system that progressively converts laser light wavelengths, distributing the energy conversion process and associated heat generation across multiple interfaces and layers, thereby reducing thermal concentration and preventing phosphor inactivation.
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 improves color uniformity and increases the chromaticity range of output light by scattering laser light and converting it into isotropically distributed fluorescence, reducing heat generation and preventing phosphor inactivation, thus providing a white light emitting device with enhanced performance.
Implementation Method 1
a phosphor layer including a phosphor for converting the laser light into light having a longer wavelength than that of the laser light
Implementation Method 2
The phosphor layer includes a plurality of concave parts, each having a depth of 50% or more and 80% or less with respect to a film thickness of the phosphor layer and an opening width of 50 μm or more, on a surface of the phosphor layer
Data Source
AI summary
A wavelength conversion member converts a wavelength of laser light. The wavelength conversion member includes a substrate having reflectivity with respect to the laser light, and a phosphor layer including a phosphor for converting the laser light into light having a longer wavelength than that of the laser light, the phosphor layer being on the substrate. The phosphor layer includes a plurality of concave parts, each having a depth of 50% or more and 80% or less with respect to a film thickness of the phosphor layer and an opening width of 50 μm or more, on a surface of the phosphor layer, the surface irradiated with the laser light. A distance between adjacent concave parts of the plurality of concave parts is smaller than a spot diameter of the laser light to be emitted to the surface of the phosphor layer.