Light Emitting Module With Partially Diffusive Reflective Layer
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Solution Overview
Problem
Existing light emitting modules with luminescent layers directly on top of LEDs suffer from poor recycling efficiency due to low reflectance of back mirrors and high refractive index of light emitters, leading to non-uniform light output and thermal distribution, while remote luminescent layers are bulky and costly, limiting their use in size-constrained applications.
Innovation Solution
A light emitting module with a partially diffusive reflective layer that has a higher base reflection coefficient than the solid state light emitter reflection coefficient, positioned at a specific distance from the light emitters to enhance light recycling and reduce thermal hot spots, using a gap between the emitter and the reflective layer to improve efficiency and prevent photosaturation of luminescent materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the luminescent layer is provided directly on top of the light emitters, then the device size is reduced, but the light recycling efficiency deteriorates due to limited reflectance of back mirrors and high refractive index of light emitters
Solution Approach 1:
The patent changes the optical parameters of the base surface by applying a reflective coating with high reflectance (greater than 90%) at the base, creating a parameter difference between the base and the light emitter surfaces. This allows efficient light recycling while maintaining compact device size, resolving the contradiction between small size and high light recycling efficiency.
2Device complexity
If the luminescent layer is provided directly on top of the light emitters, then the device structure is simplified, but the light output uniformity deteriorates resulting in hot spots
Solution Approach 1:
The patent applies local quality by creating a specific geometric configuration where the base has a larger surface area than the light emitter array, and the luminescent layer is positioned at a specific height above the light emitters. This local structural optimization ensures uniform light distribution across the luminescent layer while maintaining overall structural simplicity.
3Loss of energy
If a remote luminescent layer is used to improve light recycling efficiency, then the light output uniformity improves, but the device size increases becoming bulky
Solution Approach 1:
The patent optimizes the vertical distance parameter between the light emitter array and the luminescent layer, positioning it at a specific height that balances light recycling efficiency with compact device size. This parameter optimization allows the device to achieve high light recycling efficiency without becoming bulky, resolving the contradiction between these two requirements.
4Volume of moving object
If the luminescent layer is positioned close to the light emitters, then the device is compact, but the phosphor layer gets hot and photosaturation occurs limiting luminescent performance
Solution Approach 1:
The patent transitions from a two-dimensional close proximity arrangement to a three-dimensional configuration by positioning the luminescent layer at a specific height above the light emitters, creating vertical separation. This dimensional change allows the device to remain compact while reducing thermal load on the phosphor layer through increased spacing, resolving the contradiction between compact size and temperature control.
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 results in a more efficient light emitting module with improved light output uniformity, reduced thermal issues, and cost-effectiveness, allowing for use in size-constrained applications without the bulkiness and high material costs associated with remote luminescent layers.
Implementation Method 1
a partially diffusive reflective layer... which has diffuse reflective properties wherein at least a part of incident light is diffusively reflected
Implementation Method 2
The LED emits light of a first color towards the luminescent layer... Another portion of the emitted light is converted by the luminescent layer into light of a second color
Implementation Method 3
a transparent thermal conductor layer
Data Source
Figure 1a~1b
Figure 2a~2b
Figure 3a~3b
AI summary
A light emitting module (150) emits light through a light exit window (104) and comprises a base (110), a solid state light emitter (154, 158) and a partially diffusive reflective layer (102). The base (110) has a light reflective surface (112) which faces towards the light exit window (104). The light reflective surface (112) has a base reflection coefficient Rbase which is defined by a ratio between the amount of light that is reflected by the light reflective surface and the amount of light that impinges on the light reflective surface. The solid state light emitter (154, 158) emits light of a first color range (114), comprises a top surface (152, 158) and has a solid state light emitter reflection coefficient R_SSL which is defined by a ratio between the amount of light that is reflected by the solid state emitter (154,156) and the amount of light that impinges on the top surface (152, 158) of the solid state light emitter (1154, 156). A largest linear size dssL of the top surface (106) of the at least one solid state light emitter is defined as the longest distance from a point on the top surface (152, 158) of the at least one solid state light emitter to another point on the top surface (152, 158) of the at least one solid state light emitter along a straight line. The light exit window (104) comprises at least a part of the partially diffusive reflective layer (102). A solid state light emitter area ratio rhoSSL is defined as the ratio between the area of the top surface of the at least one solid state light emitter and the area of the light reflective surface of the base. A gap with a distance h is present between the top surface (152, 158) of the at least one solid state light emitter (154, 156) and the partially diffusive reflective layer (102). A relatively efficient light emitting module is obtained if 0.3.dSSL <= h <= 5.dSSL for 0 < rhoSSL < 0.1, 0.15.dSSL <= h <= 3.dSSL for 0.1 <= rhoSSL <= 0.25, and 0.1.dSSL <= h <= 2.dSSL for rhoSSL > 0.25, and if the value of the base reflection coefficient Rbase is larger than 70% and larger than the solid state light emitter reflection coefficient R_SSL.