Scattering Reflector for LED Light Distribution
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Solution Overview
Problem
Conventional light emitting devices using LED chips face limitations in light emission efficiency due to insufficient reflectance, particularly when trying to uniformly distribute light from the LED chip to the phosphor layer, which restricts the enhancement of light emission efficiency.
Innovation Solution
A light emitting device design featuring a reflector with a scattering surface, where at least 50% of the reflecting surface has a mean square inclination between 0.003 and 0.03, enhancing light distribution and emission efficiency by forming a random light return to the phosphor layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If mirror polishing is performed on the reflecting member to increase regular reflectance, then the surface roughness Ra becomes about 5 μm and regular reflectance is increased, but light emission efficiency enhancement is insufficient because light from the LED chip does not uniformly reach the phosphor layer
Solution Approach 1:
The patent applies local quality by creating a reflector surface with non-uniform scattering properties. Specifically, the surface is designed with controlled roughness where different regions have different scattering characteristics, allowing light to be redistributed uniformly across the phosphor layer while maintaining high reflectance. This resolves the contradiction by making the surface intentionally non-uniform to achieve uniform light distribution and improve light emission efficiency.
Solution Approach 2:
The patent employs preliminary action by pre-structuring the reflector surface with specific roughness characteristics before light interaction occurs. The surface is manufactured with predetermined scattering properties that will automatically distribute light uniformly when illuminated, eliminating the need for additional light redistribution mechanisms and enhancing light emission efficiency from the outset.
2Loss of energy
If a regular reflecting surface is used to increase reflectance, then the surface can be easily manufactured with mirror polishing, but the light distribution to the phosphor layer is non-uniform, limiting light emission efficiency enhancement
Solution Approach 1:
The patent applies parameter changes by modifying the surface roughness parameter of the reflector. Instead of maintaining a smooth mirror surface, the surface roughness is controlled within a specific range (Ra of about 0.01 μm to 10 μm) to create scattering effects. This parameter change transforms the reflector from a simple mirror into an active light redistribution element, improving light emission efficiency while remaining manufacturable through conventional polishing techniques.
3Volume of moving object
If the light emitting device is miniaturized to achieve space saving, then the device size is reduced, but the light distribution and emission efficiency become more difficult to optimize
Solution Approach 1:
The patent applies local quality in miniaturized devices by creating localized scattering centers on the reflector surface. Even in compact configurations, the controlled surface roughness ensures that light from the LED chip is scattered and redistributed uniformly across the phosphor layer, maintaining high light emission efficiency despite the reduced device size and limited space for optical components.
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 design significantly improves light emission efficiency, particularly for ultraviolet light emitting LED chips, enabling the production of high-brightness, small-sized light emitting devices suitable for backlights and illumination, while also contributing to energy savings and miniaturization.
Implementation Method 1
A portion of 50% or more in an area ratio of the reflecting surface of the reflector is formed as a scattering surface with a mean square inclination (Δq) (0.1 mm) in a range of not less than 0.003 nor more than 0.03
Data Source
AI summary
A light emitting device 1 includes a light emitting diode, a phosphor layer containing phosphors that emit a visible light by being excited by a light emitted from the light emitting diode, and a reflector disposed to surround the light emitting diode. A portion of 50% or more in an area ratio of a reflecting surface of the reflector is formed as a scattering surface with a mean square inclination (Δq) (0.1 mm) in a range of not less than 0.003 nor more than 0.03.