LED Phosphor Structure With Absorptive Edge for Near-Field Contrast
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Solution Overview
Problem
Existing light emitting devices face reduced near-field contrast due to stray light scattered by submounts, phosphor sidewalls, and side emission, which is detrimental for applications like camera flash modules and automotive front lighting.
Innovation Solution
A thin light absorptive region is defined around the edges of the light emitting surface using a light reflective material, such as SiO2, Y2O3, or TiO2, with a binding agent like silicone rubber, and a gap is created between the phosphor structure and the absorptive region to enhance contrast by preventing direct side emission and absorbing residual light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If reflective material is used to cover sidewalls to minimize light waste, then light extraction efficiency is improved, but near-field contrast ratio deteriorates due to stray light scattering
Solution Approach 1:
The patent applies different optical properties to different regions: the majority of sidewalls are covered with reflective material to maximize light extraction, while a specific localized region (the light absorptive region) is treated with light-absorbing properties to eliminate stray light. This spatial differentiation of material properties resolves the contradiction between overall light extraction efficiency and local near-field contrast ratio.
Solution Approach 2:
The light absorptive region acts as an intermediary element between the reflective sidewalls and the viewing area. It intercepts and absorbs stray light that would otherwise scatter and degrade near-field contrast, while allowing the reflective material to continue functioning for light extraction. This mediator component resolves the contradiction by managing the light paths between the two competing requirements.
2Object-affected harmful factors
If overmold side coat process is used to encapsulate LED and phosphor sidewalls, then near-field contrast is improved by reflecting side emitted light, but stray light from submount and phosphor sidewalls still reduces contrast
Solution Approach 1:
The patent segments the sidewall treatment into distinct functional zones: an overmold side coat region for reflecting light back into the phosphor, and a separate light absorptive region for capturing stray light from the submount and phosphor sidewalls. This segmentation allows each region to perform its specific function optimally, resolving the contradiction between reflecting useful light and absorbing harmful stray light.
Solution Approach 2:
The patent converts the harmful stray light generated by the submount and phosphor sidewalls into a controllable element by introducing the light absorptive region. This region specifically targets and absorbs the harmful stray light, transforming the problem of stray light generation into a solved issue through dedicated absorption, while preserving the beneficial light reflection from the overmold side coat.
3Ease of manufacture
If phosphor sidewall is partially exposed during bead blast processing, then cleaning is achieved, but light transmission through phosphor sidewall reduces near-field contrast
Solution Approach 1:
The light absorptive region serves as an intermediary that compensates for the necessary phosphor sidewall exposure during manufacturing. By positioning this absorptive region adjacent to the exposed phosphor sidewalls, it captures the light that would otherwise transmit through the partially exposed areas and degrade near-field contrast, thus resolving the contradiction between manufacturing accessibility and optical 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 significantly improves the near-field contrast ratio by reflecting side-emitted light back into the phosphor structure and absorbing residual light, thereby minimizing stray light and enhancing the performance of light projection systems.
Implementation Method 1
reflective materials can be used to reflect side emitted light back into the phosphor structure
Implementation Method 2
A light absorptive region is defined in the light reflective material around a perimeter of the light emitting surface of the phosphor structure
Data Source
AI summary
A light emitting device includes an LED having a light emitting top surface and sidewalls. A phosphor structure is attached to the light emitting surface of the LED. The phosphor structure has a light emitting top surface facing away from the LED light emitting surface, and sidewalls. A light reflective material is arranged to cover the sidewalls of the LED and the phosphor structure. A light absorptive region is defined in the light reflective material around a perimeter of the light emitting surface of the phosphor structure. The light absorptive region may be spaced apart from the perimeter of the phosphor structure by a gap. The light absorptive region may be formed by ultraviolet laser illumination of the light reflecting material.