LED Light Scattering Layer for Uniform White Emission
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Solution Overview
Problem
White light emitting LEDs with phosphor layers suffer from non-uniform emission profiles, leading to higher correlated color temperature and a 'yellow ring' effect at small emission angles, which existing solutions attempt to address through increased scattering, resulting in reduced efficiency due to light reflection losses.
Innovation Solution
Incorporating a light scattering layer between the phosphor and filter layers with a refractive index difference of Δn ≥0.2, and a product of thickness and refractive index of 1900 nm ≥ n*D ≥ 400 nm, along with a dielectric filter layer that partially reflects light rays between 400 nm to 500 nm based on emission angle, to enhance uniformity and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a light scattering layer is introduced to improve color uniformity over angles, then the emittance profile uniformity is improved, but light reflection losses increase reducing package efficiency
Solution Approach 1:
The patent optimizes the refractive index of the light scattering layer (1.4-1.8) and controls the product of thickness and refractive index (400-1900 nm) to achieve effective light scattering while minimizing reflection losses. This parameter optimization resolves the contradiction by finding the optimal balance between scattering effectiveness and transmission efficiency.
Solution Approach 2:
The patent uses composite structures including the light scattering layer combined with phosphor layer and filter layer, where each layer has specific optical properties. The light scattering layer may contain scattering particles or have a specific microstructure that provides scattering function while maintaining controlled optical impedance matching with adjacent layers.
2Illumination intensity
If the refractive index difference between light scattering layer and filter layer is increased to enhance scattering, then scattering effectiveness is improved, but light transmission is reduced
Solution Approach 1:
The patent specifies that the refractive index difference Δn between the light scattering layer and the filter layer should be ≥0.2, and the product of thickness and refractive index should be 400-1900 nm. These parameter constraints optimize the balance between scattering effectiveness and light transmission, preventing excessive reflection losses while maintaining adequate scattering function.
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 increases package efficiency for color uniformity over angles, allowing a wider range of surface roughness and improved color targeting capability, while minimizing light losses and maintaining transparency.
Implementation Method 1
the difference in refractive index Δn between the light scattering layer and the material of the filter layer adjacent to the light scattering layer is Δn ≥0.2, preferably Δn ≥0.3 and; the difference in refractive index Δn between the light scattering layer and the material of the layer adjacent to the light scattering layer in the direction of the LED isΔn ≥0.2, preferably Δn ≥0.3
Implementation Method 2
the filter layer is developed in such a manner that light rays with a wavelength of about 400 nm to 500 nm, preferably of about 420 nm to 490 nm, emitted from the LED die are at least partially reflected depending on their emission angle
Implementation Method 3
a phosphor layer that is stimulated by the blue emission of the LED into emitting yellow/red light, the combination of the yellow/red and blue emissions providing a white light
Data Source
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AI summary
The invention relates to a LED assembly comprising a light scattering layer provided between the phosphor layer of the LED and a filter layer.