Robert Lutwak said:
Blue LEDs were not on the market yet in 1995. They were invented in about
1998 and mad eit to the market (in record time) by about 2000. It must be
a bulb with a blue cover.
Robert: I would agree that the light in the Climate Control is not an LED,
but they got to market a little sooner than 2000. I tinker around with some
of these and make some lights for my Grandkids to play with. ( they think
its pretty cool & its a good mental excersize for me.) I offer the
following for your perusal.
Commercially viable blue LEDs based on the wide bandgap semiconductor
gallium nitride were invented by Shuji Nakamura while working in Japan at
Nichia Corporation in 1993 and became widely available in the late 1990s.
They can be added to existing red and green LEDs to produce white light.
Most "white" LEDs in production today use a 450nm - 470nm blue GaN (gallium
nitride) LED covered by a yellowish phosphor coating usually made of cerium
doped yttrium aluminium garnet (YAG:Ce) crystals which have been powdered
and bound in a type of viscous adhesive. The LED chip emits blue light, part
of which is converted to yellow by the YAG:Ce. The single crystal form of
YAG:Ce is actually considered a scintillator rather than a phosphor. Since
yellow light stimulates the red and green receptors of the eye, the
resulting mix of blue and yellow light gives the appearance of white.
White LEDs can also be made by coating near ultraviolet (NUV) emitting LEDs
with a mixture of high efficiency europium based red and blue emitting
phosphors plus green emitting copper and aluminium doped zinc sulfide
(ZnS:Cu,Al). This is a method analogous to the way fluorescent lights work.
The newest method used to produce white light LEDs uses no phosphors at all
and is based on homoepitaxially grown zinc selenide (ZnSe) on a ZnSe
substrate which simultaneously emits blue light from its active region and
yellow light from the substrate.
Harold