# Nichia LEDs: Angry blue tint



## o0o (Jul 21, 2007)

Are Nichia 5mm LEDs still rated at less than 500 hours to 50% lumen maintenance?

Finally, my main gripe, why can't Nichia make a white LED?

The "white" Nichia based LEDs I own ALL have an angry blue tint in the middle of the beam. This really bugs me, especially on pricey lights like my Arc AAA. 

Why can't Nichia make a 5mm LED that actually resembles white--like Luxeon and Cree are doing?


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## nikon (Jul 21, 2007)

In testing here on CPF, Nichia seemed to be the only brand of LED whose output did not deteriorate with time, even when overdriven. It appears that they're the best-built 5mm LED available. 

Their LED's also come in another bin which leans toward a yellowish tint. I prefer these over the blue and I wonder why more manufacturers don't use them. 

By the way, the blue tinted ones aren't really angry, just in a bit of a snit. It'll pass.


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## o0o (Jul 21, 2007)

Do you have a link to the test thread?


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## PhotonBoy (Jul 21, 2007)

'White' LEDs are made with a blue light emitting die coated with a yellow substance that glows intensely when exposed to blue light. The blue and yellow light mixes and simulates 'white' color. By using slightly less yellow material, I would assume that a greater amount of light gets emitted from the LED, hence you have a brighter LED at the expense of it being angry blue. JMHO.


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## o0o (Jul 22, 2007)

PhotonBoy said:


> 'White' LEDs are made with a blue light emitting die coated with a yellow substance that glows intensely when exposed to blue light. The blue and yellow light mixes and simulates 'white' color. By using slightly less yellow material, I would assume that a greater amount of light gets emitted from the LED, hence you have a brighter LED at the expense of it being angry blue. JMHO.



How are Luxeon and Cree making very bright white LEDs without the angry blue tint?

What does Luxeon and Cree do correctly that Nichia fails?


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## Martini (Jul 22, 2007)

Much of the improvement the XR-E offered over the LuxIII was due to a much thinner, more uniform phosphor layer. The 100 lumen Rebels show a similar reduction in phosphor thickness. Nichia's improvements have mostly been in the efficiency of their dice; they'll probably catch up on phosphor technology eventually.


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## SemiMan (Jul 25, 2007)

Martini said:


> Much of the improvement the XR-E offered over the LuxIII was due to a much thinner, more uniform phosphor layer. The 100 lumen Rebels show a similar reduction in phosphor thickness. Nichia's improvements have mostly been in the efficiency of their dice; they'll probably catch up on phosphor technology eventually.



One thing I do not think the XR-E has is a more uniform phosphor layer. Lumileds phosphor deposition has always been very uniform hence why they put out such a nice beam with no colored rings. The improvement of the XR-E is mostly from an improvement in the die with a form of thin-film technology. That is why their blue was also much brighter. From what I know, Nichia probably has the best phosphor knowledge in the industry. They have been doing that a very long time. I am not sure how/why you have reached your conclusions.

Semiman


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## PhotonBoy (Jul 26, 2007)

AFAIK, the 5 mm dies that Nichia uses for its LEDs are quite a bit smaller than the dies used for 1 and 3 W LEDs in Cree and Luxeon LEDs. This would make it harder to apply an even coating of yellow phosphor over the blue die. Very small imperfections in the yellow phosphor become greatly magnified when the light is shone at a white wall, revealing the angry blue of the underlying blue LED. For most purposes, the Nichia lights get the job done except for properly illuminating white walls. Unfortunately, I have a habit of trying to do this too often.


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## o0o (Jul 27, 2007)

PhotonBoy said:


> AFAIK, the 5 mm dies that Nichia uses for its LEDs are quite a bit smaller than the dies used for 1 and 3 W LEDs in Cree and Luxeon LEDs. This would make it harder to apply an even coating of yellow phosphor over the blue die. Very small imperfections in the yellow phosphor become greatly magnified when the light is shone at a white wall, revealing the angry blue of the underlying blue LED. For most purposes, the Nichia lights get the job done except for properly illuminating white walls. Unfortunately, I have a habit of trying to do this too often.



Agree that Nichia gets the job done for small tasts (requiring 1-3 lumens), such as navigating a little room.


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## Martini (Jul 27, 2007)

SemiMan said:


> From what I know, Nichia probably has the best phosphor knowledge in the industry. They have been doing that a very long time. I am not sure how/why you have reached your conclusions.


Not my conclusions, actually. Just repeating what I've read elsewhere. I suppose I should question them as well.

I agree that 5mm LEDs have their place, and they do well in that capacity. It'd to be nice to see some more improvement in tint, however; as power LEDs get better and better, the angry blue LEDs stand out more and more.


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## nikon (Jul 30, 2007)

o0o said:


> Do you have a link to the test thread?


OK, I finally located it.....http://candlepowerforums.com/vb/showthread.php?t=89759&highlight=Nichia+mjled


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## 2xTrinity (Jul 30, 2007)

> 'White' LEDs are made with a blue light emitting die coated with a yellow substance that glows intensely when exposed to blue light. The blue and yellow light mixes and simulates 'white' color. By using slightly less yellow material, I would assume that a greater amount of light gets emitted from the LED, hence you have a brighter LED at the expense of it being angry blue. JMHO.


This is actually not really true -- more light will get out (in terms of radiated power) but a blue light will not necesarily be brighter. If anything, it will often be dimmer as the eye is much, much more sensitive to the light emitted from the phosphor than it is to light from the blue die. In fact the more neutral color temp of the Cree/Lux LEDs (more like 5500K typically, as opposed to 6500K or colder) is one of the reasons they are so efficient. In fact the next generation of high-efficiency LEDs apparenly coming out from Lumileds will apparently be even warmer than that (4500K or so). More light in terms of _radiated power_ will be released with a thinner layer of phosphor, but that doesn't necessarily make it brighter. I beleive the different in sensitivity general outweighs the losses due to phosphor blockage, at least to a point.

It is true though for low-level light applications, I MUCH prefer under-driven high-power LEDs (Cree/SSC etc) to 5mm LEDs driven at the same current, specifically because the 5mm LEDs are so much bluer by comparison when viewed side-by-side.


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## The_LED_Museum (Jul 31, 2007)

White LEDs usually only turn bluish when they're overdriven; this is their way of telling you they're really pissed.






Here is an example of that angry blue color from a flashlight that really overdrives its white LEDs.


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