# WHITE -> UV ? LED with phosphor removed



## pavithra_uk (Jan 20, 2012)

Today I accidentally damaged the silicone dome of OSRAM SSL White LED.

Then I removed dome and some phosphor coating also removed with dome. remaining phosphors cleaned carefully with sharp plastic piece.

Now LED produce Bluish - Purple light. And it illuminate florescent labels, objects brightly. Looks like Near-UV

I don't have any blacklight inks or paints to test with LED. may be invisible UV illuminated paint also work with it..


Can someone explain possibility of this ? White LED with Phosphor removed can emit UV light ??


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## AnAppleSnail (Jan 20, 2012)

White LEDs are blue LEDs with phosphor on to make yellow/red/orange. Strangely, this makes white light, even if it's short red photons.

You have a blue LED. Blue LEDs have high-energy photons that make your eyes sting and make fluoro things glow. There is little or no UV in that, but you're close to the UV wavelengths.


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## CKOD (Jan 20, 2012)

More technically, they are "royal blue" LEDs usually, and usually ring in at 450nm, with normal blue being ~470 nm, and 400-350nm for most UV LEDs


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## bshanahan14rulz (Jan 21, 2012)

IIRC, GE experimented with using nearUV LEDs to excite phosphors in their vio(?) series. Perhaps this technique is still being used and it just isn't announced?


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## AnAppleSnail (Jan 21, 2012)

bshanahan14rulz said:


> IIRC, GE experimented with using nearUV LEDs to excite phosphors in their vio(?) series. Perhaps this technique is still being used and it just isn't announced?



That will take some time, because using deeper blue will shift the spectral output, shifting the CCT of the white produced to a higher value.


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## idleprocess (Jan 22, 2012)

bshanahan14rulz said:


> IIRC, GE experimented with using nearUV LEDs to excite phosphors in their vio(?) series. Perhaps this technique is still being used and it just isn't announced?



Some manufacturers experimented with the technique many years ago, such as GE and the less well-known Toyoda-Gosei. I believe they had problems with package degradation from the UV exposure. I believe the concept also suffered from lower overall efficiency than blue die + yellow phosphor technique that's now ubiquitous due to phosphor down-conversion as well as the much greater forward voltage of the LED itself.


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