# Are these LEDs a deeper blue than most?



## G12002 (Jan 3, 2012)

WP7113QBC/G (datasheet)
WP7143QBC/G (datasheet)

I found these Kingbright LEDs at Mouser while looking for a good primary blue colour (I know they exist; I've seen them everywhere). Most blue LEDs are the 470nm azure blue colour but these LEDs' datasheets rate their peak wavelength at 462nm with 465nm being the dominant. Is it likely that these are just the standard blue (the spectral graphs seem to indicate a 470nm peak) or are they deeper?


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## Harold_B (Jan 3, 2012)

The graph isn't very descriptive but I don't think it's intended to supersede the data table anyway. One consideration when specifying blue LEDs is that the manufacturers don't all list the same specs. The terms Dominant and Peak wavelengths get confused a lot but since the eye is less sensitive to wavelengths nearing the violet end of spectrum the difference is significant. This paper does a nice job explaining the definitions of the wavelength specs: http://www.instrumentsystems.com/fileadmin/editors/downloads/Products/LED_Handbook_e.pdf
Sorry if I'm telling you something you already know but for some the difference in terms is subtle and confusing. To get to the point of your question, there is little difference between an LED spec'd at 465 nm and 470 nm if both are referring to Dominant wavelength. If one is Dominant and the other is Peak then it will depend on which is which since typically the Dominant wavelength is a little higher than the Peak for blue: 465 nm Peak compared to 470 nm Dominant, not much difference; 465 nm Dominant and 470 nm Peak, significant. If you are looking for a deeper blue you are probably looking for 445 nm to 455 nm Royal Blue.


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## blasterman (Jan 4, 2012)

Also note that manufacturers build in huge amounts of lattitude when it comes to spec'ing blue bins. They may say '465', but in truth the color may be between 455-465nm if you read the fine print. Note I'm speaking in terms of dominant wavelength.

Royal is a very critical color in terms of reef lights, and this is a color were are used to dealing with. By and large royal blue Cree's stick to around 452-455nm no matter where you get them, while royal Rebels are 448-452nm. Satistronics sells a 445nm that we've verified is around 440-445nm.

Standard blue Crees and Rebels by mean sampling are around 470-475nm.

Oddly, LED's between the common royal and standard blue are tough to come by. I've tried several Asian brands that claimed 460-465nm and they were either royal or 470nm or higher. The XT-E is *supposed* to be binned very tight, but haven't found any other than typical royal.


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## G12002 (Jan 4, 2012)

Thanks for the replies so far.



Harold_B said:


> If you are looking for a deeper blue you are probably looking for 445 nm to 455 nm Royal Blue.


Thanks for the recommendation. I already have a 435nm, 450nm and a few which I estimate around 460nm or upper 450s. What I'm looking for is that nice deep non-violetish blue which seems to put the normal 470s away from the blue middle. Apparently the standard 470s peak at 466nm and the 470nm refers to its colour. Like you say it IS a subtle difference and hard to notice unless you compare them. Anyway I estimate what I'm looking for is the λDOM​ to be in the lower or mid 460s.



blasterman said:


> Also note that manufacturers build in huge amounts of lattitude when it comes to spec'ing blue bins. They may say '465', but in truth the color may be between 455-465nm if you read the fine print. Note I'm speaking in terms of dominant wavelength.
> 
> Oddly, LED's between the common royal and standard blue are tough to come by. I've tried several Asian brands that claimed 460-465nm and they were either royal or 470nm or higher.


Yeah, this is something I've come across myself even after carefully going over the datasheets. Full story (please bear with me here): A year ago I ordered a Kingbright WPL-7113PBC-Z from cpc.farnell. The vendor rated its "typical wavelength" as 465nm whatever that means. It turned out to be the standard 470nm blue despite its datasheet speccing it at 458nm peak & 465nm dom. The spectrograph in there seemed to back those numbers up. There is also apparently a L-7113PBC. Kingbright rates that with 468nm peak & 465nm dom which doesn't make sense.

My skepticism of Kingbright's data is what is keeping me from ordering those LEDs from Mouser. I don't want to make this same mistake with a delivery charge of around £12. Probably a bad idea, huh?


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## Harold_B (Jan 4, 2012)

There's always these guys: http://www.everlight.com/datasheets/Shuen3W_datasheet.pdf

Not sure where to source them where you are at but I'm sure you can find a vendor somewhere since they are one of the top 10 LED manufacturers in the world.


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## Canuke (Jan 5, 2012)

blasterman said:


> Oddly, LED's between the common royal and standard blue are tough to come by. I've tried several Asian brands that claimed 460-465nm and they were either royal or 470nm or higher. The XT-E is *supposed* to be binned very tight, but haven't found any other than typical royal.



IIRC, 460nm is the so-called "dental blue" used for curing fillings etc. Perhaps that market niche is "punching" out that notch in the supply? Most applications aren't that specific in their needs, so 470nm is usually "good enough" and that's what they will sell you -- unless you're a dentist or dental equipment supplier.


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## Harold_B (Jan 6, 2012)

Canuke said:


> IIRC, 460nm is the so-called "dental blue" used for curing fillings etc. Perhaps that market niche is "punching" out that notch in the supply? Most applications aren't that specific in their needs, so 470nm is usually "good enough" and that's what they will sell you -- unless you're a dentist or dental equipment supplier.



Could be. I would be more inclined to suspect that the wavelengths selected for manufacture are based on the excitation spectrums of highest use phosphors. Most phosphors used for LED have an excitation spectrum that peaks around 450 nm. Throw in the optimization for Stokes shift, minimizing quenching, patents (Nichia owns 405 nm phosphors and doesn't sell them to other manufacturers), etc. and you have the bulk of manufacturing at 445 - 455 nm peak wavelength. I know 455 and higher die are available but they may be used to better advantage in other products such as the cure lamps you mention or there isn't as much of a demand so there are fewer made. Just a guess but based on procuring die.


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## G12002 (Jan 6, 2012)

Harold_B said:


> There's always these guys: http://www.everlight.com/datasheets/Shuen3W_datasheet.pdf
> 
> Not sure where to source them where you are at but I'm sure you can find a vendor somewhere since they are one of the top 10 LED manufacturers in the world.


Hmm... I'm really looking for the common round T1-3/4 packages but definitely through-hole.



Canuke said:


> IIRC, 460nm is the so-called "dental blue" used for curing fillings etc. Perhaps that market niche is "punching" out that notch in the supply? Most applications aren't that specific in their needs, so 470nm is usually "good enough" and that's what they will sell you -- unless you're a dentist or dental equipment supplier.


Actually, sub-470s aren't as uncommon as you think. I can tell there's a 3mm one in my computer mouse and its manufacturer tends to use these in its other products. They are also used in signs and christmas lights. They are visibly deeper than their 470nm counterparts but remain non-violetish.

From what I read elsewhere, LEDs of the same type vary in their spectrographic properties and that there is a colour-tolerance standard imposed by their manufacturers. Could it be that these deeper blues have been made as the standard 470nm LEDs but seperated after production due to their colour variation and then repackaged?


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## anuragwap (Aug 4, 2012)

Deleted!


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