LED Filament Phosphor Layout for Incandescent-Like Appearance
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Solution Overview
Problem
LED filament lamps with traditional phosphor coatings exhibit a noticeable yellow color when off, which is aesthetically unappealing, especially in retro-styled lighting fixtures.
Innovation Solution
Employ chip scale package LEDs with reduced phosphor application, utilizing a minimal phosphor layer only on the light transmission surfaces of the LEDs, and eliminating the encapsulating phosphor to maintain the appearance of a traditional incandescent bulb.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If traditional phosphor coatings are applied to LED filament, then the LED can emit white light, but the filament exhibits a noticeable yellow color when off which is aesthetically unappealing
Solution Approach 1:
The patent applies phosphor only to specific local areas of the LED chip - namely the upper surface and sidewall surfaces - rather than coating the entire filament structure. This localized phosphor application ensures white light emission from the LED while leaving the metal stent substrate visible and free of yellow phosphor coating when the LED is not in operation.
Solution Approach 2:
The patent divides the phosphor application into separate discrete portions - an upper surface phosphor layer and sidewall phosphor layers - rather than using a continuous encapsulating phosphor coating. This segmentation allows different parts of the LED to have phosphor only where needed for light emission, while maintaining the aesthetic appearance of the metal stent when off.
2Illumination intensity
If encapsulating phosphor is used to cover the entire LED filament, then complete white light coverage is achieved, but the aesthetic appearance resembling traditional incandescent bulbs is lost
Solution Approach 1:
The patent selectively applies phosphor only to the upper surface and sidewall surfaces of the LED chips where light emission occurs, rather than encapsulating the entire filament structure. This localized approach maintains the visible metal stent substrate that resembles traditional incandescent filaments while still achieving complete white light coverage through the LED chips themselves.
Solution Approach 2:
The patent extracts and eliminates the traditional encapsulating phosphor coating that would cover the entire filament structure. By removing this full encapsulation and replacing it with localized phosphor only on LED chip surfaces, the design achieves white light emission while preserving the aesthetic appearance of exposed metal filaments similar to incandescent bulbs.
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 provides LED filaments that emit white light without a noticeable yellow hue, allowing integration into bulb designs that mimic tungsten bulbs while maintaining aesthetic appeal.
Implementation Method 1
each light emitting diode chip includes at least an upper surface that is in contact with an individual portion of phosphor
Data Source
AI summary
A light emitting filament diode that includes a filament substrate; a plurality of light emitting diodes (LEDs) electrically connected and disposed along a length of the filament substate; and a phosphorus encapsulant present in direct contact with an upper surface and sidewalls of at least one of the plurality of light emitting diodes (LEDs). No portion of phosphorus encapsulant is present overlying a portion of the filament substrate extending between the sidewalls of adjacently situated light emitting diodes having phosphorus encapsulant present thereon. The light emitting filament diode may also include a transparent encapsulant present over at least the light emitting diode chips.