Remote Phosphor LED Wavelength Conversion with Scattering Particles
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Solution Overview
Problem
Remote phosphor LED devices face issues with non-white color appearance in the OFF state, color variation with emission angle, and high costs due to the large quantity of phosphor materials required.
Innovation Solution
Incorporating a light diffusing layer with light diffractive particles, such as titanium dioxide, in direct contact with the wavelength conversion layer, which scatters excitation radiation more than phosphor-generated light, reducing the need for phosphor material and improving color uniformity and appearance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a remote phosphor wavelength conversion component is used, then the device can generate white light with high luminous efficacy, but the device appears yellowish or orange in the OFF state
Solution Approach 1:
The patent divides the wavelength conversion component into two separate layers: a wavelength conversion layer containing phosphor particles and a light diffusing layer containing diffractive particles. This segmentation allows each layer to perform its specific function independently - the phosphor layer converts blue light to yellow light for white light generation, while the diffusing layer scatters light to create a uniform white appearance in the OFF state, resolving the contradiction between luminous efficacy and appearance.
2Illumination intensity
If phosphor material is used for wavelength conversion, then blue light can be converted to yellow light, but color variation occurs with emission angle
Solution Approach 1:
The patent introduces a light diffusing layer as an intermediary between the phosphor wavelength conversion layer and the external environment. This diffusing layer acts as a mediator that scatters the converted yellow light and any remaining blue light, uniformizing the color appearance from different emission angles. The diffusing particles randomize the light paths, eliminating the directional color variation caused by the phosphor conversion process.
3Illumination intensity
If a large quantity of phosphor material is used in remote phosphor devices, then sufficient wavelength conversion can be achieved, but the cost increases significantly
Solution Approach 1:
The patent replaces the reliance on large quantities of phosphor material with an optical system - the light diffusing layer containing diffractive particles. Instead of using more phosphor to improve conversion efficiency, the diffusing layer optically enhances the perceived brightness and uniformity by scattering light. This substitution reduces phosphor material consumption while maintaining or improving the overall 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 solution enhances the white appearance in the OFF state, reduces color variation with emission angle, and decreases the required amount of phosphor material by up to 40%, while maintaining luminous efficacy.
Implementation Method 1
a light diffusing layer comprising particles of a light diffractive material... wherein the particles will scatter excitation radiation relatively more than they will scatter light generated by the at least one phosphor material
Implementation Method 2
a wavelength conversion layer comprising particles of at least one photoluminescence material and a light diffusing layer comprising particles of a light diffractive material
Data Source
AI summary
A light emitting device comprises at least one solid-state light source (LED) operable to generate excitation light and a wavelength conversion component located remotely to the at least one source and operable to convert at least a portion of the excitation light to light of a different wavelength. The wavelength conversion component has at least one photoluminescence material and a light scattering material, where the light scattering material has an average particle size that is selected such that the light scattering material will scatter excitation light from a radiation source relatively more than the light scattering material will scatter light generated by the photoluminescence material.