Light Emitting Module with Partially Diffusive Reflective Layer
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Solution Overview
Problem
Existing light emitting modules face inefficiencies due to poor recycling of light back to LEDs, non-uniform light output, and high material costs, particularly with luminescent layers directly on top of LEDs, while remote luminescent layers are bulky and costly, and struggle with heat dissipation.
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, allowing for efficient light recycling and reduced absorption, and a gap between the light emitter and the luminescent layer to improve light output and thermal management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the luminescent layer is provided directly on top of the light emitter, then the device size is reduced, but light recycling efficiency deteriorates due to poor reflectance and high absorption
Solution Approach 1:
A reflective layer is introduced as an intermediary component between the light emitter and the luminescent layer. This reflective layer has a reflection coefficient greater than 90%, significantly improving light recycling by reflecting unused light back to the light emitter for re-emission, thereby resolving the energy loss issue while maintaining the compact device structure.
Solution Approach 2:
The invention changes the optical parameter (reflection coefficient) of the interface between the light emitter and luminescent layer by introducing a highly reflective layer. This parameter change from typical metal reflectance (~70%) to enhanced reflectance (>90%) dramatically improves light recycling efficiency without increasing device volume.
2Device complexity
If the luminescent layer is provided directly on top of the light emitter, then the device structure is simplified, but hot spots form due to non-uniform light distribution
Solution Approach 1:
The reflective layer is selectively positioned at the interface between the light emitter and luminescent layer, creating a localized optical enhancement zone. This local modification improves light distribution uniformity at the critical interface without requiring complex structural changes throughout the entire device, thereby preventing hot spot formation while maintaining overall structural simplicity.
3Loss of energy
If a remote luminescent layer is used, then light recycling efficiency is improved, but the device size increases and material costs rise
Solution Approach 1:
Instead of using a full remote luminescent layer configuration, the invention applies a partial solution by placing a highly reflective layer only at the critical interface region. This partial action achieves the essential light recycling benefit without requiring the extensive structural modifications and large distances associated with complete remote luminescent layer designs, thus avoiding increased device size and material costs.
4Quantity of substance
If the luminescent layer is directly on the light emitter, then material costs are reduced, but phosphor conversion efficiency deteriorates due to high flux density and heating
Solution Approach 1:
The reflective layer serves as a thermal and optical intermediary between the light emitter and phosphor layer. It reflects unused light back to the emitter for re-emission with reduced flux density, preventing excessive heating and maintaining optimal phosphor conversion efficiency while keeping material costs low through the use of standard phosphor materials.
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 light recycling and output efficiency, reduces thermal hotspots, and lowers material costs by optimizing the reflection coefficients and structural design, resulting in a more uniform and efficient light emission.
Implementation Method 1
A light emitting module with a partially diffusive reflective layer that has a higher base reflection coefficient than the solid state light emitter, allowing for efficient light recycling
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
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, 156 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 i 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, 156 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 154, 156. The light exit window 104 comprises at least a part of the partially diffusive reflective layer 102. A solid state light emitter area ratio ?SSL 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 relatively efficient light emitting module is obtained if Rbase > R_SSL + c*(1 - R_SSL) and the factor c is 0.2 = c = 1 for 0 SSL SSL = 0.25, and 0.4 = c = 1 for ?SSL > 0.25.