Active solid-state devices (e.g. – transistors – solid-state diode – Incoherent light emitter structure – In combination with or also constituting light responsive...
Reexamination Certificate
2003-07-14
2004-08-10
Clark, S. V. (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Incoherent light emitter structure
In combination with or also constituting light responsive...
C257S081000
Reexamination Certificate
active
06774401
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a wavelength conversion LED such as a white light emitting diode in which blue light is emitted from a pn junction interface, this blue light is made incident on a fluorescent body to extract yellow light, and white light is emitted by mixing the blue light and yellow light, or alternatively, ultra-violet light is emitted from the pn junction interface and this ultra-violet light is made incident on the fluorescent body to extract intermediate colored light such as white light.
2. Detailed Description of the Prior Art
FIG. 6
shows a white LED as an example of a wavelength conversion LED known in the prior art.
In
FIG. 6
, a white LED
1
contains a white reflector
2
having a bowl
2
a
formed so as to open upward, a LED chip
3
disposed close to the center of the bowl
2
a
of the reflector
2
, and an enclosing resin
4
containing wavelength conversion material
4
a
filled into the bowl
2
a.
The reflector
2
has electrode terminals
2
b
,
2
c
which are integrated into a single body by an insert molding or the equivalent.
The LED chip
3
is formed so as to constitute a blue LED chip through the joining of InGaN (p-type) and Sic (n-type), and the pn junction surface
3
a
which constitutes the light emitting layer thereof is disposed in the expanded area near the upper edge.
In the LED chip
3
, the n-side thereof is electrically connected to the electrode terminal
2
b
exposed at the bottom of the bowl
2
a
of the reflector
2
while being fixed by, for example, a conductive adhesive; and the electrode
3
b
on the surface of the p-side thereof is connected by a wire
3
c
of metal or the like to the other electrode terminal
2
c
exposed at the bottom of the bowl
2
a.
The enclosing resin
4
comprises a translucent resin and contains fluorescent a body
4
a
which emit yellow light when exposed to blue light. As the fluorescent the body
4
a
generally have a larger specific gravity than the enclosing resin
4
, as a result of settling, the lower section thereof comprises a dense fluorescent body layer
4
b
as shown in the figure.
In the white LED
1
configured as described above, when a drive voltage is applied between the n-side and the p-side of the LED chip
3
by the electrode terminals
2
b
,
2
c
, blue light L
1
is emitted from the junction surface
3
a
thereof. The blue light L
1
emitted from the LED chip
3
is directed towards the opening and bottom of the bowl
2
a
of the reflector
2
and is approximately uniformly incident thereto.
The blue light L
1
directed towards the opening of the bowl
2
a
of the reflector
2
is emitted upwards as it is.
Meanwhile, the blue light L
1
directed towards the bottom of the bowl
2
a
of the reflector
2
is incident on the fluorescent body layer
4
b
which has settled at the bottom of the bowl
2
a
. Accordingly, the fluorescent bodies
4
a
within the fluorescent body layer
4
b
absorb the blue light L
1
, and as a result of excitation, emit yellow light L
2
in the form of fluorescent light. This yellow light L
2
is mixed with the blue light L
1
emitted upwards as it is from the opening as previously described, white light is produced overall; and this is emitted upward.
In contrast, a white LED
5
configured as shown in
FIG. 7
is also known in the prior art.
In
FIG. 7
, the white LED
5
differs in construction with the white LED
1
from
FIG. 6
in terms of the vertically-inverted disposition of the LED chip
3
; consequently, the pn junction surface
3
a
of the LED chip
3
is disposed toward the bottom within the fluorescent body layer
4
b
of fluorescent bodies
4
a
in the enclosing resin
4
.
Similarly, in the white LED
5
configured as described above, a portion of the blue light emitted at the junction surface of the LED chip
3
is absorbed by the fluorescent body
4
a
as it is passed through the fluorescent body layer
4
b
, and yellow light is emitted; in addition, the remaining portion of the blue light becomes transparent inside the LED chip
3
through the enclosing resin
4
above the fluorescent body layer
4
b
, and is emitted upwards from the enclosing resin
4
.
As a result of this, the yellow light and blue light as described above are mixed, and white light is emitted upwards.
The following problems have been experienced with configurations characterized by the white LEDs
1
,
5
as described above.
In both of the white LEDs
1
,
5
, a portion of the blue light is emitted upwards as it is from the opening in the bowl
2
a
of the reflector
2
, and in order to obtain white light, yellow light with a light volume which counterbalances the light volume of this excessively-strong blue light is required. Accordingly, the volume of fluorescent bodies
4
a
which convert blue light to yellow light must be increased. Since the blue light and the yellow light are shielded by the fluorescent body particles, therefore, the volume of light which may be extracted at the opening of the bowl drops, and the overall light emitting efficiency of the white LEDs
1
,
5
is reduced.
Furthermore, in the case of the LED chip which emits ultra-violet light, a mixture of fluorescent bodies which emit red, green, and blue light is often used; however, since ultra-violet light is emitted from the top of the chip directly to the opening in the bowl without being incident on the fluorescent bodies in this case also, this light does not contribute to the strength of the visible light extracted from the top, and the light emitting efficiency is reduced.
The similar type of problem occurs in other wavelength conversion LED with same configuration whose fluorescent body composition or the LED chip are modified to emit single colored, infrared, or intermediate colored light.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a wavelength conversion LED which improves light emitting efficiency through the use of a simple configuration.
This object is achieved by the LED of the first embodiment of the present invention comprising electrode terminals, a LED chip, a reflector having a bowl reflecting the light emitted from the LED chip to an opening, a enclosing resin filled into the bowl, and a wavelength conversion material mixed into the enclosing resin, absorbing the light emitted from the LED chip, and emitting light with a longer wavelength than that of the absorbed light, and characterized in that the LED chip is connected to a electrode terminal inside the bowl, and in addition, a conductive reflective member for reflecting the light emitted from the junction surface without transparency thereof on the substantially whole surface is provided at the top surface of the LED chip; the density of the wavelength conversion material mixed into the enclosing resin is larger below the junction surface of the LED chip than thereabove; and/or a wavelength conversion material layer is formed into a prescribed shape on the inside surface of the reflector with the bowl.
In this first embodiment, light is emitted from the junction surface of the LED chip as a result of application of drive voltage from both electrode terminals to the LED chip via the conductive reflective member and is reflected downward by the conductive reflective member.
All or some of the downward directed light is absorbed by the wavelength conversion layer, and wavelength converted light is emitted there.
Accordingly, when the color of the light emitted by the LED chip is blue, the blue light which is not absorbed by the wavelength conversion layer is mixed with the yellow light emitted by the wavelength conversion layer, and is emitted from the top to the exterior as white light. Furthermore, when ultra-violet light is emitted by the LED chip, this ultra-violet light is converted by the wavelength conversion layer and emitted to the exterior as white light. Consideration has been given for diodes which emit non-white light using combinations of wavelength conversion material and LED chip emission wavelength, f
Aoki Dai
Kagiwada Masataka
Nakada Konosuke
Oba Hayato
Clark S. V.
Dickstein Shapiro Morin & Oshinsky LLP.
Stanley Electric Co. Ltd.
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