Subject: Blue LEDs

From: [email-masked] (Ian Ashdown)
Date: 24 May 1995 11:20:20 -0400

A few days ago, Jeff Sani of Ledalite asked for information about blue
light-emitting diodes. The ensuing discussion gravitated towards exit
sign colors, leaving some of his questions unanswered.

While you may not see blue LEDs in commercial products, they do exist.
In December 1993, Nichia Chemical Company (Japan) announced the develop-
ment of a high-efficiency blue LED. At 3.6 lumens per watt, it is 100
times more efficient than previously available products. The peak wave-
length is 450 nm.

In June 1994, Eagle-Picher Industries (Miami, OK) and North Carolina
State University (Raleigh, NC) announced the development of a blue LED
with a peak wavelength of 489 nm and 1.7 lumens per watt.

To put these developments into perspective, lumen/watt ratings for
other state-of-the-art LED designs are 8.0 lm/W (red @ 650 nm),
20 lm/W (yellow @ 585 nm) and 18.0 lm/W (green @ 512 nm).

Those interested in further details (including references) should read:

Cook, J. W. Jr., and J. F. Schetzina. 1995. "Blue-Green Light-Emitting
Diodes Promise Full-Color Displays," Laser Focus World 31(3):101-104
(March).

On a related issue, there are electroluminescent organic emissive
films. Unlike light-emitting diodes that require expensive semicon-
ductor manufacturing techniques, these organic light-emitting devices
(OLEDs, first demonstrated in 1987) are cheap and easy to manufacture
using vapor deposition or spin coating techniques. Red, green, blue,
yellow and white OLEDs have been fabricated.

Again, those interested in further details should read:

Forrest, S. R., P. E. Burrows, and M. E. Thompson. 1995. "Organic
Emitters Promise a New Generation of Displays," Laser Focus World
31(2):99-107 (February).

While it is unlikely that these devices will replace conventional
fluorescent-tube technology in architectural lighting applications,
the same was said of fluorescent versus incandescent lamp technology
when the first fluorescent lamps were still laboratory curiosities.
Rather than saying "man will never fly," we should at least keep
abreast of the limits of lighting research as we do our everyday
work in lighting design.

So why did Jeff Sani post his questions to the 'net rather than ask
me? Well, I was on holidays ... ;^)

Ian Ashdown, P. Eng.
Research & Development Manager
Ledalite Architectural Products, Inc.
9087A - 198th Street
Langley, B.C.
Canada V3A 4P8
Ian Ashdown, P. Eng.                      THIS SPACE PURPOSEFULLY LEFT BLANK
Research & Development Manager
Ledalite Architectural Products Inc.
9087A - 198th Street
Langley, British Columbia
Canada V3A 4P8

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From: [email-masked] (John MacDonald)
Date: 26 May 1995 10:34:08 -0300

In article <[email-masked]>, [email-masked] (Ian Ashdown) says:
> etc. etc.

I would have to disagree with Ian assessment of the impact of blue LEDs
on the lighting industry.  Red LEDs have been making tremedous in-roads
into the automotive industry in such places as turning lights and 
brakelights.  As these types of applications increase we should see a 
marked increase in the candela output of such LED devices.  Furthermore, 
with the emergence of blue LEDs (blue+red+green makes white I believe) we 
will probably see a "white" LED within the next five years.  This source of
white light has the potential to be very small compared to traditional
incandescent and fluorescent lighting not to mention much more efficient.
As with red and green LEDs, once the big boys in compact disk and CD ROM 
players get into the game, not to mention the auto industry, I think we 
"see" realistic white LEDs emerging in the market place within 10-15
years.  Comments?

***********************************************
... and crawling on the planet's face
	some insects called the human race...
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From: "Jennifer M. Skolones" <[email-masked]>
Date: 26 May 1995 13:58:27 GMT

[email-masked] (John MacDonald) wrote:

> Furthermore, 

>From  the catalog of Ledtronics, of Torrance CA:

"Full spectrum 5mm integrated RGB LEDs offer a wide variety of color
combinations, including white, for indicators, displays, spectral
analysis, color synthesis and other applications."

Near as I can tell, the "white" LED is here now.

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From: [email-masked] (Parapsycho)
Date: 1 Jun 1995 11:57:53 -0400

A company called Gillway (I believe that's how you spell it) has white and
blue LED's  I will post the address and phone number when I get it.

Cya!

Mike
Mike Parker