Feit LED filament bulb with white filaments

[PhotonWrangler]

I ran across this curiosity yesterday, a clear A19 LED filament bulb where the filaments appear snow-white when off. The coating makes the filaments appear a little bit thicker than the yellow ones, although this could be just an illusion. I purchased the 2700k version out of curiosity. When turned on it looks more like 3000k to me, which I prefer.

Shining a UV light into the clear glass globe reveals a dim reddish glow from the filaments. This might be a result of the glass blocking the 365nm UV wavelength so I can't tell if the white coating is actually the phosphor layer or not, at least not without breaking the glass.

The white filaments make the bulb look less obtrusive when it's off - it kind of blends into the surroundings. Interesting concept. I wonder if it affects the bulb's efficiency in any way.

**Edit** Aimed a blue LED at the white filaments and got a small amount of pinkisk-white fluorescence out of them.

 

[angerdan]

Where did you ran across it?
Which brand is it?
Is there a photo or website where it can be seen?

 

[PhotonWrangler]

I found them at a DIY store in the U.S. Here is their page describing the new white LED filaments. It probably won't be long before other manufacturers copy this design.

 

[PhotonWrangler]

Update: I found the patent that describes what's going on here. They start with a traditional yellow phosphor coating on the blue LED die, then they add an overcoat of a "scattering agent" that produces the white appearance when they're off. This overcoat can include an additional phosphor for further color tuning.