U.S. patent application number 12/036058 was filed with the patent office on 2011-05-26 for thermal management systems for light emitting devices and systems.
This patent application is currently assigned to Luminus Devices, Inc.. Invention is credited to Daniel Yen Chu, Alexei A. Erchak, Michael A. Joffe, Robert F. Karlicek, JR., Paul Panaccione, Warren P. Pumyea, Brian L. Stoffers, Joseph D. Whitney.
Application Number | 20110121703 12/036058 |
Document ID | / |
Family ID | 39710402 |
Filed Date | 2011-05-26 |
United States Patent
Application |
20110121703 |
Kind Code |
A1 |
Karlicek, JR.; Robert F. ;
et al. |
May 26, 2011 |
THERMAL MANAGEMENT SYSTEMS FOR LIGHT EMITTING DEVICES AND
SYSTEMS
Abstract
One or more embodiments presented herein include a light
emitting system and/or device that can include a thermal management
system. The thermal management system can provide for transport
and/or dissipation of heat generated by a light emitting
device.
Inventors: |
Karlicek, JR.; Robert F.;
(Chelmsford, MA) ; Chu; Daniel Yen; (Andover,
MA) ; Whitney; Joseph D.; (Merrimack, NH) ;
Panaccione; Paul; (Newburyport, MA) ; Pumyea; Warren
P.; (Gardner, MA) ; Stoffers; Brian L.;
(Billerica, MA) ; Joffe; Michael A.; (Harvard,
MA) ; Erchak; Alexei A.; (Cambridge, MA) |
Assignee: |
Luminus Devices, Inc.
Billerica
MA
|
Family ID: |
39710402 |
Appl. No.: |
12/036058 |
Filed: |
February 22, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60903184 |
Feb 23, 2007 |
|
|
|
Current U.S.
Class: |
313/46 ;
29/428 |
Current CPC
Class: |
G02B 6/0018 20130101;
G02F 2201/36 20130101; G02B 6/0085 20130101; Y10T 29/49826
20150115; G02F 1/133615 20130101; G02F 1/133628 20210101; G02B
6/0028 20130101 |
Class at
Publication: |
313/46 ;
29/428 |
International
Class: |
H01J 61/52 20060101
H01J061/52; B23P 11/00 20060101 B23P011/00 |
Claims
1. A light emitting system comprising: an illumination component; a
solid-state light emitting device configured to emit light into the
illumination component; and a heat spreading component associated
with the illumination component, the heat spreading component
having a first thermal conductivity in a first direction
substantially larger than a second thermal conductivity in a second
direction.
2. The light emitting system of claim 1, further comprising one or
more heat pipes and/or vapor plates disposed under the heat
spreading component.
3. The light emitting system of claim 2, wherein the one or more
heat pipes and/or vapor plates are in thermal communication with
the light emitting device.
4. The light emitting system of claim 3, further comprising fins
disposed in thermal communication with at least some of the one or
more heat pipes and/or vapor plates.
5. The light emitting system of claim 1, wherein the heat spreading
component comprises a graphite material.
6. The light emitting system of claim 1, wherein the heat spreading
component has an in-plane thermal conductivity greater than about
400 W/mK.
7. The light emitting system of claim 1, wherein the heat spreading
component has an out-of-plane thermal conductivity less than about
20 W/mK.
8. The light emitting system of claim 1, further comprising one or
more out-of-plane thermal conduction channels disposed to penetrate
at least a portion of a out-of-plane thickness of the heat
spreading component, wherein the out-of-plane conduction channels
are configured to have thermal conductivity substantially larger
than the out-of-plane thermal conductivity of the heat spreading
component.
9. The light emitting system of claim 8, wherein the one or more
out-of-plane thermal conduction channels comprise metal.
10. The light emitting system of claim 8, further comprising one or
more heat pipes and/or vapor plates in thermal communication with
the light emitting device, wherein the one or more out-of-plane
thermal conduction channels are in thermal communication with at
least some of the one or more heat pipes and/or vapor plates.
11. The light emitting system of claim 1, further comprising one or
more liquid crystal layers disposed over the illumination
component.
12. The light emitting system of claim 1, wherein the first
direction is substantially parallel to a majority of the light
transmitted through the illumination component.
13. The light emitting system of claim 1, wherein the heat
spreading component has an in-plane thermal conductivity and an
out-of-plane thermal conductivity, wherein the thermal conductivity
in the first direction is the in-plane thermal conductivity and the
thermal conductivity in the second direction is the out-of-plane
thermal conductivity.
14. The light emitting system of claim 1, wherein the heat
spreading component is disposed under the illumination
component.
15. The light emitting system of claim 1, wherein the first thermal
conductivity is greater than ten times the second thermal
conductivity.
16. The light emitting system of claim 1, wherein the first thermal
conductivity is greater than twenty times the second thermal
conductivity.
17. The light emitting system of claim 1, wherein the first
direction is perpendicular to the second direction.
18. The light emitting system of claim 1, wherein the solid-state
light emitting device is in thermal communication with the heat
spreading component.
19. The light emitting system of claim 18, wherein the solid-state
light emitting device is directly on the heat spreading
component.
20. A method of forming a light emitting system comprising:
providing an illumination component; providing a solid-state light
emitting device configured to emit light into the illumination
component; and providing a heat spreading component associated with
the illumination component, the heat spreading component having a
first thermal conductivity in a first direction substantially
larger than a second thermal conductivity in a second direction.
Description
RELATED APPLICATIONS
[0001] This application claims priority under 35 U.S.C.
.sctn.119(e) to U.S. Provisional Application Ser. No. 60/903,184,
filed on Feb. 23, 2007, which is herein incorporated by reference
in its entirety.
INCORPORATION BY REFERENCE
[0002] This application incorporates by reference the following
U.S. patents and patent application Publications: U.S. Pat. No.
7,211,831 based on U.S. Ser. No. 10/723,987, entitled "Light
Emitting Devices," and filed Nov. 26, 2003; U.S. Pat. No. 7,098,589
based on U.S. Ser. No. 10/724,029, entitled "Light Emitting
Devices," and filed Nov. 26, 2003; US 20070045640 based on U.S.
Ser. No. 11/210,262, entitled "Light Emitting Devices for Liquid
Crystal Displays," and filed Aug. 23, 2005; US 20060043391 based on
U.S. Ser. No. 11/210,261, entitled "Light Emitting Devices for
Liquid Crystal Displays," and filed Aug. 23, 2005; US 20060043400
based on U.S. Ser. No. 11/209,905, entitled "Polarized Light
Emitting Device," and filed Aug. 23, 2005; US 20070085082 based on
U.S. Ser. No. 11/323,176, entitled "Light-Emitting Devices and
Related Systems," and filed Dec. 30, 2005; U.S. Ser. No.
11/323,332, entitled "Light-Emitting Devices and Related Systems,"
and filed Dec. 30, 2005; US 20070211182 based on U.S. Ser. No.
11/413,609, entitled "Optical System Thermal Management Methods and
Systems," and filed Apr. 28, 2006; US 20070211183 based on U.S.
Ser. No. 11/413,968, entitled "LCD Thermal Management Methods and
Systems," and filed Apr. 28, 2006; US 20070211184 based on U.S.
Ser. No. 11/429,649, entitled "Liquid Crystal Display Systems
Including LEDs," and filed May 5, 2006; US 20070267642 based on
U.S. Ser. No. 11/521,092, entitled "Light-Emitting Devices and
Methods for Manufacturing the Same," filed Sep. 14, 2006; and US
20080019147 based on U.S. Ser. No. 11/600,548, entitled "LED Color
Management and Display Systems" filed Nov. 16, 2006.
FIELD
[0003] The present embodiments are drawn generally towards light
emitting devices and/or systems, and more specifically to light
emitting devices and/or systems that include thermal management
systems. Specifically, the methods and systems of at least some of
the embodiments include light emitting diodes that generate
light.
BACKGROUND
[0004] A light emitting diode (LED) can often provide light in a
more efficient manner than an incandescent light source and/or a
fluorescent light source. The relatively high power efficiency
associated with LEDs has created an interest in using LEDs to
displace conventional light sources in a variety of lighting
applications. For example, in some instances LEDs are being used as
traffic lights and to illuminate cell phone keypads and
displays.
[0005] Typically, an LED is formed of multiple layers, with at
least some of the layers being formed of different materials. In
general, the materials and thicknesses selected for the layers
influence the wavelength(s) of light emitted by the LED. In
addition, the chemical composition of the layers can be selected to
promote isolation of injected electrical charge carriers into
regions (commonly referred to as quantum wells) for relatively
efficient conversion to optical power. Generally, the layers on one
side of the junction where a quantum well is grown are doped with
donor atoms that result in high electron concentration (such layers
are commonly referred to as n-type layers), and the layers on the
opposite side are doped with acceptor atoms that result in a
relatively high hole concentration (such layers are commonly
referred to as p-type layers).
[0006] LEDs also generally include contact structures (also
referred to as electrical contact structures or electrodes), which
are features on a device that may be electrically connected to a
power source. The power source can provide current to the device
via the contact structures, e.g., the contact structures can
deliver current along the lengths of structures to the surface of
the device within which energy can be converted into light.
SUMMARY
[0007] Light emitting devices, and related components, systems, and
methods associated therewith are provided. Related components
and/or systems can include thermal management systems.
[0008] In one aspect, a light emitting system is provided. The
system comprises an illumination component and a solid-state light
emitting device configured to emit light into the illumination
component. The system further includes a heat spreading component
associated with the illumination component. The heat spreading
component having a first thermal conductivity in a first direction
substantially larger than a second thermal conductivity in a second
direction.
[0009] In another aspect, a method of forming a light emitting
system is provided. The method comprises providing an illumination
component; providing a solid-state light emitting device configured
to emit light into the illumination component; and providing a heat
spreading component associated with the illumination component. The
heat spreading component has a first thermal conductivity in a
first direction substantially larger than a second thermal
conductivity in a second direction.
[0010] Other aspects, embodiments and features of the invention
will become apparent from the following detailed description of the
invention when considered in conjunction with the accompanying
figures. The accompanying figures are schematic and are not
intended to be drawn to scale. In the figures, each identical or
substantially similar component that is illustrated in various
figures is represented by a single numeral or notation.
[0011] For purposes of clarity, not every component is labeled in
every figure. Nor is every component of each embodiment of the
invention shown where illustration is not necessary to allow those
of ordinary skill in the art to understand the invention. All
patent applications and patents incorporated herein by reference
are incorporated by reference in their entirety. In case of
conflict, the present specification, including definitions, will
control.
BRIEF DESCRIPTION OF FIGURES
[0012] FIG. 1a is a schematic drawing of a light emitting system
according to one embodiment;
[0013] FIG. 1b is a schematic drawing of a light emitting system
according to one embodiment;
[0014] FIG. 2 is a schematic drawing of a side-view of a light
emitting system according to one embodiment;
[0015] FIG. 3 is a schematic drawing of a top-view of the light
emitting system of FIG. 2 according to one embodiment;
[0016] FIG. 4 is a schematic drawing of a top-view of part of a
light emitting system according to one embodiment;
[0017] FIG. 5 is a schematic drawing of a top-view of a light
emitting system according to one embodiment;
[0018] FIG. 6 is a schematic drawing of a side-view of a light
emitting system according to one embodiment;
[0019] FIG. 7 is a schematic drawing of a side-view of a light
emitting system according to one embodiment;
[0020] FIG. 8 is a schematic drawing of a side-view of a light
emitting system according to one embodiment;
[0021] FIG. 9 is a schematic drawing of a top-view of part of the
light emitting system of FIG. 8 according to one embodiment;
[0022] FIG. 10 is a schematic drawing of a side-view a light
emitting system according to one embodiment;
[0023] FIG. 11 is a schematic drawing of a bottom-view of part of
the light emitting system of FIG. 10 according to one
embodiment;
[0024] FIG. 12 is a schematic drawing of a perspective-view of the
light emitting system of FIG. 10 according to one embodiment;
[0025] FIG. 13 is a schematic drawing of a heat spreading component
according to one embodiment;
[0026] FIG. 14 is a schematic drawing of a side-view a light
emitting system according to one embodiment;
[0027] FIG. 15 is a schematic drawing of a side-view of part of a
light emitting system according to one embodiment;
[0028] FIG. 16 is a schematic drawing of a side-view of part of a
light emitting system according to one embodiment;
[0029] FIG. 17 is a schematic drawing of a perspective-view of part
of the light emitting system of FIG. 16 according to one
embodiment;
[0030] FIG. 18 is a schematic drawing of a side-view of a light
emitting system according to one embodiment;
[0031] FIG. 19 is a schematic drawing of a side-view of a light
emitting system according to one embodiment;
[0032] FIG. 20 is a schematic drawing of a side-view of a light
emitting system according to one embodiment;
[0033] FIG. 21 is a schematic drawing of a side-view of a light
emitting system according to one embodiment;
[0034] FIG. 22 is a schematic drawing of a side-view of a light
emitting system according to one embodiment;
[0035] FIG. 23 is a schematic drawing of a perspective-view of a
display system according to one embodiment;
[0036] FIG. 24 is a schematic drawing of a back-view of a display
system according to one embodiment;
[0037] FIG. 25 is a schematic drawing of a light emitting die
according to one embodiment.
DETAILED DESCRIPTION
[0038] One or more embodiments presented herein include a light
emitting system and/or device that can include a thermal management
system. The thermal management system can provide for transport
and/or dissipation of heat generated by a light emitting device. In
some embodiments, the ability to remove heat from the light
emitting device can enable operation at high power levels (e.g.,
light emitting devices having a total light output power of greater
than 0.5 Watts). Due to potential for the high output power light
emission from the light emitting devices, the number of light
emitting devices that are used per unit length of an illumination
component may be reduced (e.g., one red-green-blue die set per
greater than about 2 inches).
[0039] FIG. 1a illustrates a light emitting system 100 including an
illumination component 110 and a heat spreading component 120
disposed under the illumination component 110. A light emitting
device 130 may be configured to emit light into the illumination
component 110. The light emitting device 130 may be in thermal
communication with a thermal conductor component 140.
[0040] In some embodiments, the thermal conductor component 140 may
comprise one or more heat pipes and/or one or more vapor plates.
The thermal conductor component 140 may alternatively and/or
additionally comprise one or more metal components having a desired
shape. The one or more metal components may include copper,
aluminum, and/or any other metal components. The one or more metal
components may be in thermal communication with the one or more
heat pipes and/or one or more vapor plates. In some embodiments the
thermal conductor component 140 may comprise materials having
anisotropic thermal conductivity. For example, thermal conductor
component 140 may comprise graphite and/or graphite related
materials, including but not limited to graphite sheets, graphite
fibers, graphite composites, and/or graphite foams. Graphite
composites, for example, may include a graphite component (e.g.,
fiber, sheet, particles) within a matrix of another material (e.g.,
polymeric material, epoxy).
[0041] In some embodiments, the heat spreading component 120 may
have anisotropic thermal conductivity. In some embodiments the heat
spreading component 120 may have a thermal conductivity in a first
direction (e.g., an in-plane thermal conductivity) that is
substantially larger than the thermal conductivity in a second
direction (e.g., an out-of-plane thermal conductivity). For
example, the thermal conductivity in the first direction may be
greater than two times the thermal conductivity in the second
direction; in some cases, the thermal conductivity in the first
direction may be greater than five times, greater than ten times,
or greater than twenty times, the thermal conductivity in the
second direction.
[0042] In some embodiments the thermal conductivity of the heat
spreading component 120 in the first direction (e.g., in-plane
thermal conductivity) is greater than about 200 W/mK (e.g., greater
than about 300 W/mK, 400 W/mK, 500 W/mK). In some embodiments the
thermal conductivity in the second direction (e.g., out-of-plane
thermal conductivity) of the heat spreading component 120 is less
than about 50 W/mK (e.g., less than about 40 W/mK, 30 W/mK, 20
W/mK, 10 W/mK).
[0043] In some embodiments, the heat spreading component may be
associated with the illumination component. For example, the heat
spreading component may be disposed between at least a portion of
the thermal conductor component 140 and at least a portion of the
illumination component 110. As illustrated in FIG. 1a, at least a
portion of the thermal conductor component 140, as indicated by a
portion 141 of the thermal conductor component 141, may be disposed
under the illumination component 110. The heat spreading component
120 may be disposed between portion 141 of the thermal conductor
component 140 and the illumination component 110. The heat
spreading component 120 may possess substantially low out-of-plane
thermal conductivity (e.g., less than about 50 W/mK, less than
about 40 W/mK, 30 W/mK, 20 W/mK, 10 W/mK) so as to prevent any
substantial amount of heat in portion 141 of the thermal conductor
component 140 being transferred to the illumination component 110.
The heat spreading component 120 may possess substantially high
in-plane thermal conductivity (e.g., greater than about 200 W/mK,
300 W/mK, 400 W/mK, 500 W/mK) so as to facilitate the in-plane
spreading of any heat transferred from the thermal conductor
component 140 to the heat spreading component 120. In this manner,
the heat spreading component 120 may both thermally insulate the
illumination component 110 from heat present in thermal conduction
component 140, and therefore may inhibit the formation of hot spots
on the illumination component 110. Hotspots on illumination
component 110 may be detrimental, as the optical emission
properties of illumination component 110 may alter as a function of
local temperature. As such, the heat spreading component 120 may
provide for substantially uniform temperature across the
illumination component 110. For example, the temperature variation
across the illumination component may be within 5.degree. C.
[0044] In some embodiments, heat spreading component 120 may be
attached to the thermal conductor component 141 and/or the
illumination component via an attachment material. The attachment
material may include an adhesive. The attachment material between
the heat spreading component and the thermal conductor component
and/or the illumination component may facilitate the assembly of
the light emitting system.
[0045] In some embodiments, other components may be disposed
between the illumination component 110 and the heat spreading
component 120. A thermal insulator may be disposed between
illumination component 110 and the spreading component 120. In some
embodiments, other components may be disposed between the heat
spreading component 120 and the thermal conduction component 140.
For example, a thermal insulator may be disposed between heat
spreading component 120 and thermal conduction component 140.
[0046] Light emitting device 130 may be any light emitting device
including solid state light emitting devices such as light emitting
diode and laser diode. In some embodiments, it is preferred that
the light emitting device is a light emitting diode (i.e., LED). As
used herein, a light emitting device may be a light emitting die, a
partially packaged light emitting die, or a fully packaged light
emitting die. It should be understood that a light emitting device
may include two or more light emitting dies associated with one
another, for example a red-light emitting die, a green-light
emitting die, a blue-light emitting die, a cyan-light emitting die,
or a yellow-light emitting die. For example, the two or more
associated light emitting dies may be mounted on a common package.
The two or more light emitting dies may be associated such that
their respective light emissions may be combined to produce a
desired spectral emission. The two or more light emitting dies may
also be electrically associated with one another (e.g., connected
to a common ground).
[0047] In some embodiments light emitting device at 130 may be
attached to thermal conduction component 140 via a thermally
conductive attachment material. The attachment material may include
thermally conductive epoxy, solder, eutectic bonding metals, and/or
other attachment materials, as the techniques presented are not
limited in this respect.
[0048] Illumination component 110 may be a component that
transports, homogenizes, scatters, and emits light from one or more
of its surfaces. In the embodiment shown in FIG. 1a, illumination
component 110 emits light via surface 111 (represented by arrows
132). Illumination component 110 may be edge lit via light emitted
(arrows 131) by light emitting device 130.
[0049] However, it should be appreciated that the techniques
presented herein are not limited to edge lit systems, and may
include back lit optical components, as illustrated for system 110b
of FIG. 1b. In such embodiments, light emitting devices may be
disposed on a thermal conduction component. A heat spreading
component 120 may be disposed over the assembly of the light
emitting devices on the thermal conduction component. Holes through
the heat spreading component 120 may be arranged to be disposed
over the light emitting devices, thereby enabling light emitted by
the light emitting devices to propagate through the heat spreading
component 120 and onto optical component 110 which may be disposed
over the heat spreading component 120.
[0050] FIG. 2 illustrates a side-view of an embodiment of a light
emitting system 200. System 200 may include a light emitting device
130 attached to a mount 142. Mount 142 may comprise a metal
component, including but not limited to a metal block (e.g.,
copper, aluminum). One or more heat pipes and/or one or more vapor
plates 143 may in thermal communication with mount 142. The one or
more heat pipes and/or one or more vapor plates 143 may be attached
to the mount 142 via a thermally conductive attachment material,
such as a solder and/or a thermally conductive epoxy. Mount 142 may
include holes 145 (e.g., having a circular cross-section, an
elliptical cross-section, a rectangular cross-section) within which
one or more heat pipes and/or one or more vapor plates 143 may be
partially (or completely) inserted therein. Protrusions 144, such
as one or more fins, may be in thermal communication with one or
more heat pipes and/or vapor plates 143. Additionally, or
alternatively, protrusions 144 may be in thermal communication with
mount 142. Protrusions 142 may provide for substantially large
surface area that can provide for substantial heat dissipation
(e.g., transmission of heat to the ambient atmosphere).
[0051] Illumination component 110 may include an illumination panel
that can extend over a desired area. Illumination component 110 may
include a light guide 112. Light guide 112 may be optically
transparent and/or opaque layer 112. Light guide 112 may, in part
or in whole, be formed of glass, PMMA, and/or other suitable
materials. Light guide 112 may include scattering centers and/or
features (e.g., surface features on a top and/or bottom side) that
may scatter light out of the light guide 112 (as represented by
arrows 132). Scattered light may be emitted via emission surface
111. The density of the scattering centers and/or features within
and/or on the light guide can varied along the length of the light
guide 112, thereby allowing for the tuning of the percentage (at a
given length along the guide) of the total light emitted from the
light guide. In one embodiment, the density of scattering centers
and/or features as a function of the length along the light guide
can be selected to allow for substantially uniform light emission
along the length of the light guide. Illumination component 110 may
include a reflector 114 disposed on the backside 113 of the light
guide 112. In some embodiments, reflector 114 may be absent and
light is substantially confined to the interior of the light guide
112 based substantially on principles of total internal reflection
of light within the light guide.
[0052] Illumination component 110 may include a mixing region 115.
Mixing region 115 can mix and/or homogenize light. In some
embodiments, light emitting device 130 can be configured such that
the emitted light is coupled into mixing region 115 of the
illumination component 110.
[0053] A heat spreading component 120 may be disposed between the
one or more heat pipes and/or vapor plates 143 and the illumination
component 110. The heat spreading component may include a material
having an in-plane thermal conductivity that is substantially
larger than an out-of-plane thermal conductivity, as described
above. For example, the thermal conductivity in the first direction
may be greater than two times the thermal conductivity in the
second direction; in some cases, the thermal conductivity in the
first direction may be greater than five times, greater than ten
times, or greater than twenty times, the thermal conductivity in
the second direction. In some embodiments the in-plane thermal
conductivity of the heat spreading component 120 is greater than
about 200 W/mK (e.g., greater than about 300 W/mK, 400 W/mK, 500
W/mK). In some embodiments the out-of-plane thermal conductivity of
the heat spreading component 120 is less than about 50 W/mK (e.g.,
less than about 40 W/mK, 30 W/mK, 20 W/mK, 10 W/mK). The heat
spreading component 120 may include graphite, including but not
limited to graphite sheets, graphite fibers, and/or graphite foams.
In some embodiments, the heat spreading component may include a
graphite layer disposed between the illumination panel 110 and the
heat pipes and/or vapor plates 143.
[0054] FIG. 3 illustrates a top view of the light emitting system
200. The top-view corresponds to the view of the illumination panel
110 from the light emission surface 111. The heat spreading
component 120 may be disposed under a portion or all of the
illumination panel 110. The heat spreading component 120 may extend
beyond the illumination panel 110, as illustrated in FIG. 3.
[0055] In some embodiments, the illumination panel 110 may include
a plurality of illumination blades 110a-z that may be arranged to
lie adjacent to each other. The plurality of illumination blades
may form the illumination panel 110. In some embodiments, an
illumination blade may be illuminated (e.g., via one or more edges)
by one or more light emitting devices. In the illustrated system of
FIG. 4, light emitting devices 130a, b, c, . . . z illuminate
illumination blades 110a, b, c, . . . z, respectively.
[0056] In some embodiments, one or more of the heat pipes and/or
vapor plates 143 may be arranged such that their lengths lie at a
non-zero angle (.theta.) with respect to a horizontal side 118 of
the illumination panel 110. The angle .theta. between the lengths
of the heat pipes and/or vapor plates 143 and the horizontal side
118 of the illumination panel 110 may be greater than about
5.degree. (e.g., greater than about 10.degree., greater than about
20.degree., greater than about 30.degree., greater than about
40.degree., greater than about 50.degree., greater than about
60.degree.). In some embodiments, the mount 142 is arranged to lie
parallel to a vertical side 119 of the illumination panel 110.
[0057] In some embodiments, the illumination panel 110 is arranged
vertically such that the vertical side 119 of the illumination
panel 110 is substantially parallel to the gravitational force (g).
When arranged in such a manner, the non-zero angle (.theta.)
arrangement for the heat pipes and/or vapor plates 143 may cause
working fluid within the heat pipes and/or vapor plates 143 to
experience a gravitational force that can facilitate the return of
condensed water to the end of the heat pipes and/or vapor plates
closer to the light emitting device heat sources.
[0058] FIG. 4 illustrates a top-view of part of a light emitting
system 300 wherein heat pipes and/or vapor plates 143 have varying
lengths and/or cross-sectional diameters. Varying properties for
the heat pipes and/or vapor plates can be used to facilitate heat
dissipation to the ambient. For example, in some embodiments the
heat pipes and/or vapor plates can be configured and arranged to
have increasing thermal conduction capabilities (e.g., due to
length variations, diameter variations, and/or working fluid
variations) as a function of location along the length of the mount
142. In some embodiments, the heat pipes and/or vapor plates 143
may have increasing lengths as a function of location along the
mount 143, as illustrated in FIG. 4. In some embodiments, the heat
pipes and/or vapor plates 143 may have increasing diameters as a
function of location along the mount 143. In some embodiments, the
heat pipes and/or vapor plates 143 may have increasing diameters
and lengths as a function of location along the mount 143. One or
more of such arrangements may facilitate heat dissipation as hot
air that rises to the top of the system may contribute to increased
temperatures near the top of the system.
[0059] FIG. 5 illustrates a top-view of a light emitting system 500
having heat pipes and/or vapor plates 143 are arranged in a
vertical configuration. The heat pipes and/or vapor plates 143 are
arranged such that their lengths are substantially parallel to the
gravitational force direction. Such an arrangement can facilitate
the operation of the heat pipes and/or vapor plates. Evaporated
working fluid that may be evaporated from the bottom part of the
heat pipes and/or vapor plates 143 closer to the light emitting
devices 130 may rise to the top region of the heat pipes and/or
vapor plates 143. At the top region, the evaporated fluid may
condenses to a fluid state and flow back to the bottom region of
the heat pipe and/or vapor plate via the aid of the gravitational
force. Alternatively, or additionally, capillary action on the
inner sidewalls of the heat pipes and/or vapor plates may
facilitate the transport of the fluid back to the bottom
region.
[0060] FIG. 6 illustrates a side-view of a light emitting system
600 having an L-shaped mount 142. L-shaped mount 142 may include a
bottom portion 146 that may be attached to a top portion 147. In
some embodiments, the bottom portion 146 and the top portion 147
are formed of the same material. In some embodiments, the bottom
portion 146 and the top portion 147 are formed of the same metal
(e.g., copper, aluminum). In some embodiments, the bottom portion
146 and the top portion 147 are formed of different materials.
[0061] Bottom portion 146 may facilitate the alignment of
components placed thereon. In one embodiment, heat spreading
component 120 may be disposed over bottom portion 146. Heat
spreading component 120 may be in contact with bottom portion 146
or other components may be arranged between heat spreading
component 120 and bottom portion 146. Illumination panel 110 may be
disposed over heat spreading component 120. As previously
discussed, illumination panel 110 may include a plurality of panels
110a, b, c . . . z. Each panel may be disposed over the heat
spreading component 120. The L-shaped mount 142 may facilitate the
in-plane and/or out-of-plane alignment of the heat spreading
component and/or the illumination panel 110 (which may include
multiple panels). The L-shaped mount 142 may facilitate the
alignment of the light emitting devices 130 such that the light
emitting devices 130 can emit light into the illumination panel 110
(e.g., via the edge of the illumination panel).
[0062] Alternatively, or additionally, a mount 142 can have a shape
other than an L-shape which can be used to facilitate the alignment
of one or more components of the light emitting system. In some
embodiments, the mount has one or more slots within which
components or layers may be inserted. The mount can include a slot
for within which the heat spreading component may be inserted.
[0063] FIG. 7 illustrates a side-view of a light emitting system
700 including a heat spreading component 120 disposed under only a
portion of the illumination component 110. In some embodiments, the
illumination component 110 is an illumination panel (as shown in
the top-view FIG. 3). The light emitting system 700 can include
heat pipes and/or vapor plates 143 disposed under a portion or all
of heat spreading component 120. Protrusions 144 (e.g., fins) can
be arranged to lie under a portion or all of heat spreading
component 120. In some embodiments, the heat spreading component
120 may cover at least about 10% of the total emission area of the
illumination component 110 (e.g., at least 20% of the total
emission area, at least 30% of the total emission area, at least
50% of the total emission area, at least 70% of the total emission
area).
[0064] FIG. 8 illustrates a side-view of a light emitting system
800 including a heat spreading component 125. The heat spreading
component 125 may include a layer 127 possessing anisotropic
thermal conductivity and one or more regions 126 arranged to extend
through some or all of the out-of-plane thickness of the
anisotropic thermal conductivity layer 127. Regions 126 may have a
substantially larger (e.g., greater than two times, greater than
five times, greater than ten times) out-of-plane thermal
conductivity (e.g., greater than about 50 W/mK, greater than about
100 W/mK, greater than about 200 W/mK, greater than about 300 W/mK,
greater than about 400 W/mK) as compared to the layer 127.
[0065] In some embodiments, layer 127 may include a graphite and/or
graphite-related material. In some embodiments, regions 126 may
include metal, such as copper and/or aluminum. In some embodiments,
regions 126 may include metal protrusions and/or spikes. In some
embodiments, regions 126 may include metal screws, nails, and/or
rivets. In some embodiments, regions 126 may include a material
having an anisotropic thermal conductivity (e.g., graphite and/or
graphite related materials) orientated such that an axis (or plane)
of high thermal conductivity lies substantially along the
illustrated out-of-plane direction.
[0066] In some embodiments, another heat spreading component 120
may be disposed over heat spreading component 125. Heat spreading
component 120 can extend over a portion or all of illumination
component 110. In some embodiments, heat spreading component 120
may extend over a portion or all of heat spreading component 125.
In some embodiments, heat spreading component 125 may be disposed
under only a portion of heat spreading component 120. In some
embodiments, unlike heat spreading component 125, heat spreading
component 120 does not include one or more regions arranged to
extend through some or all of the out-of-plane thickness of an
anisotropic thermal conductivity layer where the one or more region
have a substantially larger out-of-plane thermal conductivity as
compared to the anisotropic thermal conductivity layer. In other
embodiments, heat spreading component 120 may include one or more
regions arranged to extend through some or all of the out-of-plane
thickness of an anisotropic thermal conductivity layer where the
one or more region have a substantially larger out-of-plane thermal
conductivity as compared to the anisotropic thermal conductivity
layer.
[0067] Heat spreading component 125 may be arranged such that some
or all of regions 126 may be in contact with one or more heat pipes
and/or vapor plates 143. An example of such an arrangement is
illustrated in the top view schematic of FIG. 9, where the
illumination component 110 and heat spreading component 120 are
omitted for purposes of clarity. Regions 126 of heat spreading
component 125 may have any desired shape. In the illustrated system
of FIG. 9, regions 126 have circular shapes, however it should be
appreciated that other shapes are possible, as the techniques are
not limited in this respect. In some embodiments, the regions 126
are in contact with at least about 5% of the top-view area of the
heat pipes and/or vapor plates 143 (e.g., at least 10%, at least
about 20%, at least about 30%, at least about 40%, at least about
50%).
[0068] In some embodiments, regions 126 are in contact with the
heat pipes and/or vapor plates 143 and allow for substantial
out-of-plane heat conduction. Heat transported out-of-plane via the
regions 126 can then be effectively transported in-plane via
anisotropic thermal conduction layer 127. In this manner, one or
more heat pipes and/or vapor plates can be in effective thermal
communication via regions 126 and anisotropic thermal conduction
layer 127. Such an arrangement can provide for more even heat
distribution.
[0069] FIG. 10 illustrates a side-view of a light emitting system
1000 including a heat spreading component 125 in thermal contact
with a mount 142. The heat spreading component 125 may be attached
to the mount 145 via an attachment mechanism. Heat spreading
component 125 may be inserted in a slot in mount 142. The
attachment mechanism can include one or more protrusions 148 and/or
149 that can pierce the heat spreading component 125. Protrusions
148 may be arranged on a top surface within the slot of mount 142.
Protrusions 149 may be arranged on a bottom surface within the slot
of mount 142. Protrusions 148 and/or 149 may be formed of a metal
and may be part of the mount 142. Protrusions 148 and/or 149 can
facilitate out-of-plane conduction of heat into the heat spreading
component 125 which may have an in-plane thermal conductivity that
is substantially higher than an out-of-plane thermal conductivity,
as previously described. The system can also include one or more
heat pipes and/or vapor plates (not shown) and/or one or more other
heat spreading components. In some embodiments, heat spreading
component 125 can include regions having substantially higher
out-of-plane thermal conductivity, as described for the heat
spreading component 125 of FIGS. 8 and 9.
[0070] FIGS. 11 and 12 illustrate bottom view and perspective views
of the light emitting system 1000. It should be appreciated that
the mount 142 may be formed of an integrated assembly that includes
both protrusions 148 and 149, or alternatively, the mount 142 may
be formed of separate components 142a and 142b, as illustrated in
FIG. 12. Component 142a can include protrusions 148 and component
142b can include protrusions 149. In such an embodiment, heat
spreading component 125 may be placed to overlie protrusions 149
and component 142b can be placed into a depressed region of mount
142 housing protrusions 148. Pressure can then be applied to form a
tight seal whereby heat spreading component 125 may be pierced by
protrusions 128 and/or 149.
[0071] FIG. 13 illustrates an embodiment of a heat spreading
component 1300. Heat spreading component 1300 can include
inter-digitated layers 126 and 127. Layers 127 may have an
anisotropic thermal conductivity, where, in some embodiments, the
in-plane thermal conductivity of layers 127 is substantially larger
than the out-of-plane thermal conductivity. In some embodiments the
in-plane thermal conductivity of layers 127 is greater than about
200 W/mK (e.g., greater than about 300 W/mK, 400 W/mK, 500 W/mK).
In some embodiments the out-of-plane thermal conductivity of layers
127 is less than about 50 W/mK (e.g., less than about 40 W/mK, 30
W/mK, 20 W/mK, 10 W/mK). For example, the in-plane thermal
conductivity may be greater than two times out-of plane thermal
conductivity in the second direction; in some cases, the in-plane
thermal conductivity may be greater than five times, greater than
ten times, or greater than twenty times, the out-of-plane thermal
conductivity. Layers 127 may include graphite, including but not
limited to graphite sheets, graphite fibers, and/or graphite
foams.
[0072] Layers 126 may have an out-of-plane thermal conductivity
that is substantially larger (e.g., greater than two times, greater
than five times, greater than ten times) than the out-of-plane
thermal conductivity of layers 127. In some embodiments, layers 126
have an Out-of-plane thermal conductivity greater than about 50
W/mK (e.g., greater than about 100 W/mK, greater than about 200
W/mK, greater than about 300 W/mK, greater than about 400 W/mK). In
some embodiments, regions 126 may include metal, such as copper
and/or aluminum. In some embodiments, regions 126 may include a
material having an anisotropic thermal conductivity (e.g., graphite
and/or graphite related materials) orientated such that an axis (or
plane) of high thermal conductivity lies substantially along the
illustrated out-of-plane direction.
[0073] In other embodiments, alternating layers 126 and 127 may be
arranged in any manner (e.g., a non-digitated arrangement) while
allowing for regions including layers 126 extending through at
least a portion of the out-of-plane thickness of heat spreading
component 1300.
[0074] FIG. 14 illustrates a side-view of a light emitting system
1400 including a heat spreading component 125 having protrusions
(e.g., fins) 144. Protrusions 144 may extend though a portion of
the out-of-plane thickness of heat spreading component 125.
Protrusions 144 (e.g., fins) may be formed of a material having a
substantially large out-of-plane thermal conductivity. In some
embodiments, protrusions 144 may be formed of a metal (e.g.,
aluminum and/or copper) and/or a material have substantially
out-of-plane high thermal conductivity (e.g., graphite and/or
graphite related material, such a graphite sheets, fibers, foams).
In embodiments where the protrusions (e.g., fins) 144 are formed of
a material having an anisotropic thermal conductivity, the material
may be arranged such that the a high thermal conductivity direction
is substantially parallel to the out-of-plane direction.
Protrusions (e.g., fins) 144 may facilitate dissipation of heat to
the surrounding ambient due a large surface area of the protrusions
(e.g., fins) 144.
[0075] FIG. 15 illustrates a side-view of a light emitting system
1400 including a mount 142 having one or more protrusions 148 that
can pierce the heat spreading component 125 via an edge. The
protrusions 148 may be formed of a metal (e.g., aluminum and/or
copper).
[0076] FIGS. 16 and 17 illustrate a side-view and perspective view,
respectively, of a light emitting system 1500 including a mount 142
having a slot within which heat spreading component 125 may be
inserted. An optionally separable component 142b with one or more
protrusions 148 may be arranged to pierce the heat spreading
component 125. Protrusions 148 may be formed of a metal (e.g.,
aluminum and/or copper).
[0077] FIG. 18 illustrates a side-view of a light emitting system
1800. System 1800 may include one or more light emitting devices
supported (e.g., mounted) on a thermal conductor component 140.
Thermal conductor component 140 may include a layer 127 which may
have layer 128 disposed thereover (e.g., in contact) and/or layer
129 disposed thereunder (e.g., in contact).
[0078] In some embodiments, layer 127 may have an anisotropic
thermal conductivity, where, in some embodiments, the thermal
conductivity of layer 127 along a direction parallel to layers 128
and/or 129 is substantially larger (e.g., greater than two times,
greater than five times, greater than ten times) than the thermal
conductivity of layer 127 along a direction normal to layers 128
and/or 129. In some embodiments the thermal conductivity of layers
127 along a direction parallel to layers 126 and/or 127 is greater
than about 200 W/mK (e.g., greater than about 300 W/mK, 400 W/mK,
500 W/mK). In some embodiments the thermal conductivity of layer
127 normal to layers 128 and/or 129 is less than about 50 W/mK
(e.g., less than about 40 W/mK, 30 W/mK, 20 W/mK, 10 W/mK). Layer
127 may include graphite, including but not limited to graphite
sheets, graphite fibers, and/or graphite foams.
[0079] Layers 128 and/or 129 may include metal (e.g., copper and/or
aluminum) and may provide structural stability to the thermal
conductor component 140. In this manner, the thermal conductor
component may be formed as a flat layer and may be bent to conform
to any desired shape. In some embodiments, the thermal conductor
component may form an L-shape, as illustrated in the cross-section
drawing of FIG. 18.
[0080] In some embodiments, protrusions 144 (e.g., fins) may extend
through a portion (or all) of the thickness of layer 127. In some
embodiments, protrusions 144 are formed of a metal (e.g., copper
and/or aluminum). In some embodiments, one or more regions 126 may
extend through a portion (or all) of the thickness of layer 127. In
some embodiments, regions 126 may be disposed under a region where
one or more light emitting devices may be mounted. In some
embodiments, regions 126 may be formed of a metal (e.g., copper
and/or aluminum). Regions 126 may provide for substantially large
thermal conduction along the thickness of the layer 127. Layer 127
may provide for substantially large thermal conduction along the
length of the thermal conduction component 140.
[0081] In some embodiments, a heat spreading component 120 may be
disposed over thermal conduction component 140. As previously
described, heat spreading component 120 may shield the illumination
component 110 from heat transported and/or dissipated by thermal
conduction component 140, thereby, in part or in whole, alleviating
any hotspot formation on the illumination component 110.
[0082] FIG. 19 illustrates a side-view of a light emitting system
1900 including one or more light emitting devices 130 arranged to
emit light substantially perpendicular to a length of a thermal
conductor component. In some embodiments, the thermal conductor
component includes one or more heat pipes and/or vapor plates 143
and one or more light emitting devices 130 are arranged to emit
light (represented by arrows 131) substantially perpendicular to
the lengths of some or all of the heat pipes and/or vapor plates
143. The light emitting devices 130 may be attached to the heat
pipes and/or vapor plates 143 using a suitable attachment material,
such as a thermally conductive epoxy and/or a solder.
[0083] Light emitting system 1900 may include one or more wedge
optics 135 that may have one of their input sides placed over one
or more light emitting devices 130 so as to accept light emitted by
the light emitting devices. The one or more wedge optics 135 may
include reflective regions 136 arranged at any angle (e.g., at
about a 45.degree. angle) with respect to the input sides of the
wedge optics.
[0084] In some embodiments, the reflective regions may include
surfaces coated with a reflective material, such as a metal (e.g.,
silver, aluminum). In some embodiments, the reflective regions may
include mirror stacks including one or more dielectric,
semiconductor, and/or metal layers. Mirror stacks of dielectrics,
semiconductors, and/or metal layers may be configured to provide
for substantial reflection for a range of angles of light impinging
thereon. In some embodiments, the mirror stacks may reflect at
least about 95% of the light impinging thereon (e.g., at least
about 97%, at least about 99%).
[0085] The mirror stack can have a photonic bandgap for light
having a range of wavelengths (e.g., including a range of
wavelengths including the emission wavelengths of the light
emitting devices 130). The mirror stack can have a photonic bandgap
for light having a range of propagation directions (e.g., including
a range of propagation directions including substantially all of
the propagation directions for light emitting by the light emitted
devices). In some embodiments, the mirror stack can be an
omni-directional photonic bandgap having a photonic bandgap for all
directions. Such a mirror may have very high reflectivity (greater
than about 97%, greater than about 99%) and/or substantially no
absorption (e.g., less than about 3% absorption, less than about 2%
absorption, less than about 1% absorption). The one or more wedge
optics 135 may include light output surfaces through light
reflected (arrows 133) by the reflective regions 136 may be emitted
from.
[0086] Although the illustration of FIG. 19 shows the light
emitting device arranged to emit light at an angle normal to the
heat pipe and/or vapor plates 143, other arrangements are possible.
In some embodiments, one or more light emitting devices 130 are
arranged to emit light at an angle of greater than about 20.degree.
to a surface normal of some or all of the heat pipes and/or vapor
plates (e.g., greater than about 40.degree., greater than about
60.degree., greater than about 80.degree.).
[0087] In some embodiments, the one or more wedge optics 135 may be
integrated with the illumination component 110. The one or more
wedge optics 135 may be formed of the same material as the light
guide 110 and/or the mixing region 115. FIG. 20 illustrates a
side-view of such an embodiment wherein a light emitting system
2000 includes an illumination component integrated with a wedge
optic. In the illustrated system, the wedge optic region 135 can
also serve as a mixing region, however it should be appreciated
that the wedge optic region need not be formed of the same material
as the mixing region. In some embodiments, the wedge optic region
135 may be formed of the same material as the light guide 112.
[0088] It should be appreciated that light emitting device edge-lit
backlights for illumination and/or display systems (e.g., LCD
displays), the mutual arrangement of components can limit the
overall system performance and/or size. In some systems, light
emitting devices may not be operating in their optimal thermal
regime and a large display bezel may be employed to cover a bulky
thermal path conduit. In some embodiments, coupling light from
light emitting devices into an illumination component enables
compact arrangement of parts, improved cooling efficacy, optimized
light emitting device operating conditions, and/or high overall
system performance.
[0089] As illustrated in the cross-section of the light emitting
system 2100 of FIG. 21, in some edge-lit backlight units (BLU)
(e.g., for displays, such as LCD displays), light from light
emitting devices may be coupled into an illumination component
(e.g., including a light guide layer) from the edge of the
illumination component. The light sources are thus positioned so
that their emitting surfaces are perpendicular to the plane of the
light diffuser.
[0090] Also, a large-area heat sink (e.g., including fins that can
dissipate heat to the ambient) for dissipating heat generated by
the light emitting devices is commonly placed behind and coplanar
with the illumination component. For improved cooling efficacy, a
thermal conductor component (e.g., including a mount and/or one or
more heat pipes and/or vapor plates) is typically used to carry
heat over the whole area of the heat sink. Thus, the direction of
the heat flux (arrow 149) generated by light emitting devices may
be redirected. This can be achieved by an L-shaped and/or U-shaped
thermal conduit which transports heat away from the light emitting
devices and directs it into thermal conductor component. The length
of the thermal path may therefore be a factor limiting thermal
performance of the conduit. Also, the size of the thermal conduit
may dictate the minimum size of the display bezel 180 which covers
it and surrounds the display area 190. Reducing the width of the
bezel may be desirable in display applications.
[0091] As described previously in connection with the light
emitting system illustrated in FIGS. 19 and 20, light emitting
devices may be positioned so that there emitting surface is
coplanar with a thermal conductor. A similar embodiment is
illustrated in the cross-section drawing of the light emitting
system 2200 of FIG. 22. Such an arrangement can significantly
shorten the length of the thermal path 149. A shortened thermal
path can translate into cooler light emitting device operating
temperatures, which can yield higher efficiency and/or an extended
lifetime for the light emitting devices. The absence of the
L-shaped and/or U-Shaped heat conduit can enable a reduction in the
width of the bezel.
[0092] Light from the light emitting devices can be coupled into
the illumination component 110 in the direction normal or
close-to-normal to the plane of the display 190. Light coupled into
the illumination component 110 may be redirected into the plane of
the light guiding layer by an optical reflector 136 disposed on an
angled edge.
[0093] In one embodiment, the reflector is a total internal
reflector (TIR). In one embodiment, the reflector can be an
external reflecting and/or refractive component redirecting light
into the display plane. In one embodiment, the reflector has a
shape matching the emission pattern of the light emitting devices
to effectively collimate and/or redirect light into the plane of
the illumination component. In one embodiment, the reflector
includes a metal reflective film which may be formed (e.g.,
deposited) on it to facilitate light reflection into the plane. In
one embodiment, the reflector includes a multi-layer mirror stack
(e.g., including dielectric, semiconductor, and/or metal layers).
The mirror stack layers may be formed (e.g., deposited) to
facilitate broad-spectrum light reflection into the plane. In one
embodiment, the emission pattern of the light emitting devices is
modified to light reflection into the plane of the illumination
component. In one embodiment, a phase-matching material (e.g., a
phase-matching fluid) may be located between the light emitting
device emission surface and the illumination component light input
surface so as to reduce interface optical coupling losses.
[0094] FIG. 23 illustrates a perspective view of a display system
2300. Display system 2300 may include a backlight unit 160. Display
assembly 190 (e.g., including LCD layers) may be disposed in front
of a light emission surface 161 of backlight unit 160 and may
modulate light emitted by the backlight unit 160 (arrow 132) and
output light (arrows 191) forming a desired image. Backlight unit
160 may have a thickness 162 less than about 35 mm. In some
embodiments, the backlight unit 160 has a thickness 162 less than
about 25 mm (e.g., less than about 20 mm, less than about 15 mm,
less than about 10 mm). In some embodiments, the backlight unit 160
may substantially thinner than the backlight units including cold
cathode fluorescent tubes (CCFL).
[0095] One or more light emitting devices 130 can be arranged to
emit light into backlight unit 160. In one embodiment, the one or
more light emitting devices 130 can be arranged to emit light into
an illumination component (not shown) of the backlight unit 160.
The illumination component can include an illumination panel
including light mixing regions and/or light guiding region that may
include scattering centers that scatter light propagating within
the illumination panel (e.g., within a total internal reflection
angle) out of the panel via light emission surface 161.
[0096] Display system 2300 may include electronics modules, which
may include power supply 192, thin-film transistor (TFT) display
electronics 194, and/or video electronics 196 arranged as units
over regions of the backside of the backlight unit 160. The
electronics modules (e.g., power supply 192, TFT electronics 194,
video electronics 196) may have thicknesses (e.g., thickness 193,
195, 197, respectively) of less than about 3 inches (e.g., less
than about 2 inches, less than about 1 inches).
[0097] Display system 2300 may include a thermal management module
170 that may transport and/or dissipate heat generated by the light
emitting devices 130. In some embodiments, the thermal management
module 170 may have thickness 171 of less than or equal to largest
thicknesses of the electronics modules (e.g., power supply 192, TFT
electronics 194, video electronics 196). Thermal management module
170 may have a thickness of less than about 3 inches (e.g., less
than about 2 inches, less than about 1 inches). Thermal management
module 170 may be arranged so as to cover a portion of the backside
area of the backlight unit 160. In some embodiments, thermal
management module 170 may cover less than about 75% of the backside
area of the backlight unit 160 (e.g., less than about 50%, less
than about 25%, less than about 10%). Thermal management module 170
may be placed over a different backside area of the backlight unit
160 than the electronics modules (e.g., power supply 192, TFT
electronics 194, video electronics 196).
[0098] FIG. 24 illustrates a back view of a display system 2400
including a thermal management module 170 which can transport
and/or dissipate heat generated by light emitting devices that can
illuminate backlight unit 160. Thermal management module 170 may
include thermal conduction segment 172 which may be connected to
thermal dissipation zone 173. Thermal dissipation zone 173 may be
connected to thermal dissipation zone 175 via thermal conduction
segment 174. In some embodiments, thermal dissipation zones may
include protrusions (e.g., fins) that can provide for heat
dissipation via the ambient. The protrusions (e.g., fins) may
include thermal conductive material(s) and/or components (e.g.,
metals such as aluminum and/or copper, graphite sheets, graphite
fibers, graphite foams, heat pipes, vapor plates). Thermal
conduction segments 173 and/or 174 may be formed of thermally
conductive materials and/or components (e.g., metals such as
aluminum and/or copper, graphite sheets, graphite fibers, graphite
foams, heat pipes, vapor plates).
[0099] It should be appreciated that although the system 2400 is
illustrated as having two heat dissipation zones, any number of
heat dissipation zones with any number of thermal conduction
segments are possible. Also, a given heat dissipation zone may be
connected one or more other heat dissipation zones via one or more
heat conduction segments. Such arrangements of heat dissipation
zones and/or heat conduction segments can allow for a thermal
management module 170 to conform to any arrangement of modules 199
(e.g., electronics modules) for a backside of a display.
[0100] In some embodiments, cooling fluid may flow through chambers
in one or more components of a light emitting system. Chambers for
the flow of cooling fluid may be present within a mount of one or
more light emitting devices. In some embodiments, the cooling fluid
may be forced to flow within the cooling chambers via passive
and/or active approaches. Passive flow of cooling fluid may occur
due to temperature differences experienced by the cooling fluid
from one region to another region. In some embodiments, an active
cooling component (e.g., a fan, a micro-speaker, a pump) may
facilitate cooling of one or more components (e.g., protrusions,
such as fins, heat pipes and/or vapor plates, mounts) of the light
emitting system. In some embodiments, a Stirling engine may be used
to harness at least a portion of the heat generated by one or more
light emitting devices and perform work. The work performed by the
Stirling engine may include operating a pump that may circulate a
cooling fluid (e.g., within chambers in a light emitting device
mount) and facilitate cooling of the light emitting devices. The
work performed by the Stirling engine may include operating a fan
to circulate air.
[0101] In some embodiments, one or more light emitting devices may
include light emitting dies that may be directly attached to a
thermal management system which may include a mount and/or one or
more heat pipes and/or vapor plates and/or one or more heat
spreading components. In some embodiments, one or more light
emitting dies may be supported by a package that may be attached to
the thermal management system.
[0102] Light emitting devices (e.g., devices 130) of embodiments
presented may include light emitting diodes and/or laser
diodes.
[0103] FIG. 25 illustrates a light emitting diode (LED) die that
may be the light generating component of the light emitting device,
in accordance with one embodiment. It should also be understood
that various embodiments presented herein can also be applied to
other light emitting devices, such as laser diodes, and LEDs having
different structures (such as organic LEDs, also referred to as
OLEDs). The LED 31 shown in FIG. 25 comprises a multi-layer stack
131 that may be disposed on a support structure (not shown). The
multi-layer stack 131 can include an active region 134 which is
formed between n-doped layer(s) 135 and p-doped layer(s) 133. The
stack can also include an electrically conductive layer 132 which
may serve as a p-side contact, which can also serve as an optically
reflective layer. An n-side contact pad 136 is disposed on layer
135. It should be appreciated that the LED is not limited to the
configuration shown in FIG. 25, for example, the n-doped and
p-doped sides may be interchanged so as to form a LED having a
p-doped region in contact with the contact pad 136 and an n-doped
region in contact with layer 132. As described further below,
electrical potential may be applied to the contact pads which can
result in light generation within active region 134 and emission of
at least some of the light generated through an emission surface
138. As described further below, openings 139 may be defined in a
light emitting interface (e.g., emission surface 138) to form a
pattern that can influence light emission characteristics, such as
light extraction and/or light collimation. It should be understood
that other modifications can be made to the representative LED
structure presented, and that embodiments are not limited in this
respect.
[0104] The active region of an LED can include one or more quantum
wells surrounded by barrier layers. The quantum well structure may
be defined by a semiconductor material layer (e.g., in a single
quantum well), or more than one semiconductor material layers
(e.g., in multiple quantum wells), with a smaller electronic band
gap as compared to the barrier layers. Suitable semiconductor
material layers for the quantum well structures can include InGaN,
AlGaN, GaN and combinations of these layers (e.g., alternating
InGaN/GaN layers, where a GaN layer serves as a barrier layer). In
general, LEDs can include an active region comprising one or more
semiconductors materials, including III-V semiconductors (e.g.,
GaAs, AlGaAs, AlGaP, GaP, GaAsP, InGaAs, InAs, InP, GaN, InGaN,
InGaAlP, AlGaN, as well as combinations and alloys thereof), II-VI
semiconductors (e.g., ZnSe, CdSe, ZnCdSe, ZnTe, ZnTeSe, ZnS, ZnSSe,
as well as combinations and alloys thereof), and/or other
semiconductors. Other light emitting materials are possible such as
quantum dots or organic light emission layers.
[0105] The n-doped layer(s) 135 can include a silicon-doped GaN
layer (e.g., having a thickness of about 4000 nm thick) and/or the
p-doped layer(s) 133 include a magnesium-doped GaN layer (e.g.,
having a thickness of about 40 nm thick). The electrically
conductive layer 132 may be a silver layer (e.g., having a
thickness of about 100 nm), which may also serve as a reflective
layer (e.g., that reflects upwards any downward propagating light
generated by the active region 134). Furthermore, although not
shown, other layers may also be included in the LED; for example,
an AlGaN layer may be disposed between the active region 134 and
the p-doped layer(s) 133. It should be understood that compositions
other than those described herein may also be suitable for the
layers of the LED.
[0106] As a result of openings 139, the LED can have a dielectric
function that varies spatially according to a pattern. The
dielectric function that varies spatially according to a pattern
can influence the extraction efficiency and/or collimation of light
emitted by the LED. In some embodiments, a layer of the LED may
have a dielectric function that varies spatially according to a
pattern. In the illustrative LED 31, the pattern is formed of
openings, but it should be appreciated that the variation of the
dielectric function at an interface need not necessarily result
from openings. Any suitable way of producing a variation in
dielectric function according to a pattern may be used. For
example, the pattern may be formed by varying the composition of
layer 135 and/or emission surface 138. The pattern may be periodic
(e.g., having a simple repeat cell, or having a complex repeat
super-cell), or non-periodic. As referred to herein, a complex
periodic pattern is a pattern that has more than one feature in
each unit cell that repeats in a periodic to fashion. Examples of
complex periodic patterns include honeycomb patterns, honeycomb
base patterns, (2.times.2) base patterns, ring patterns, and
Archimedean patterns. In some embodiments, a complex periodic
pattern can have certain holes with one diameter and other holes
with a smaller diameter. As referred to herein, a non-periodic
pattern is a pattern that has no translational symmetry over a unit
cell that has a length that is at least 50 times the peak
wavelength of light generated by one or more light generating
portions. Examples of non-periodic patterns include aperiodic
patterns, quasi-crystalline patterns (e.g., quasi-crystal patterns
having 8-fold symmetry), Robinson patterns, and Amman patterns. A
non-periodic pattern can also include a detuned pattern (as
described in U.S. Pat. No. 6,831,302 by Erchak, et al., which is
incorporated herein by reference). In some embodiments, a device
may include a roughened surface. The surface roughness may have,
for example, a root-mean-square (rms) roughness about equal to an
average feature size which may be related to the wavelength of the
emitted light.
[0107] In certain embodiments, an interface of a light emitting
device is patterned with openings which can form a photonic
lattice. Suitable LEDs having a dielectric function that varies
spatially (e.g., a photonic lattice) have been described in, for
example, U.S. Pat. No. 6,831,302 B2, entitled "Light Emitting
Devices with Improved Extraction Efficiency," filed on Nov. 26,
2003, which is herein incorporated by reference in its entirety. A
high extraction efficiency for an LED implies a high power of the
emitted light and hence high brightness which may be desirable in
various optical systems.
[0108] It should also be understood that other patterns are also
possible, including a pattern that conforms to a transformation of
a precursor pattern according to a mathematical function,
including, but not limited to an angular displacement
transformation. The pattern may also include a portion of a
transformed pattern, including, but not limited to, a pattern that
conforms to an angular displacement transformation. The pattern can
also include regions having patterns that are related to each other
by a rotation. A variety of such patterns are described in U.S.
patent application Ser. No. 11/370,220, entitled "Patterned Devices
and Related Methods," filed on Mar. 7, 2006, which is herein
incorporated by reference in its entirety.
[0109] Light may be generated by the LED as follows. The p-side
contact layer can be held at a positive potential relative to the
n-side contact pad, which causes electrical current to be injected
into the LED. As the electrical current passes through the active
region, electrons from n-doped layer(s) can combine in the active
region with holes from p-doped layer(s), which can cause the active
region to generate light. The active region can contain a multitude
of point dipole radiation sources that generate light with a
spectrum of wavelengths characteristic of the material from which
the active region is formed. For InGaN/GaN quantum wells, the
spectrum of wavelengths of light generated by the light generating
region can have a peak wavelength of about 445 nanometers (nm) and
a full width at half maximum (FWHM) of about 30 nm, which is
perceived by human eyes as blue light. The light emitted by the LED
may be influenced by any patterned interface through which light
passes, whereby the pattern can be arranged so as to influence
light extraction and/or collimation.
[0110] In other embodiments, the active region can generate light
having a peak wavelength corresponding to ultraviolet light (e.g.,
having a peak wavelength of about 370-390 nm), violet light (e.g.,
having a peak wavelength of about 390-430 nm), blue light (e.g.,
having a peak wavelength of about 430-480 nm), cyan light (e.g.,
having a peak wavelength of about 480-500 nm), green light (e.g.,
having a peak wavelength of about 500 to 550 nm), yellow-green
(e.g., having a peak wavelength of about 550-575 nm), yellow light
(e.g., having a peak wavelength of about 575-595 nm), amber light
(e.g., having a peak wavelength of about 595-605 nm), orange light
(e.g., having a peak wavelength of about 605-620 nm), red light
(e.g., having a peak wavelength of about 620-700 nm), and/or
infrared light (e.g., having a peak wavelength of about 700-1200
nm).
[0111] In certain embodiments, the LED may emit light having a high
power. As previously described, the high power of emitted light may
be a result of a pattern that influences the light extraction
efficiency of the LED. For example, the light emitted by the LED
may have a total power greater than 0.5 Watts (e.g., greater than 1
Watt, greater than 5 Watts, or greater than 10 Watts). In some
embodiments, the light generated has a total power of less than 100
Watts, though this should not be construed as a limitation of all
embodiments. The total power of the light emitted from an LED can
be measured by using an integrating sphere equipped with
spectrometer, for example a SLM12 from Sphere Optics Lab Systems.
The desired power depends, in part, on the optical system that the
LED is being utilized within. For example, a display system (e.g.,
a LCD system) may benefit from the incorporation of high brightness
LEDs which can reduce the total number of LEDs that are used to
illuminate the display system.
[0112] The light generated by the LED may also have a high total
power flux. As used herein, the term "total power flux" refers to
the total power divided by the emission area. In some embodiments,
the total power flux is greater than 0.03 Watts/mm.sup.2, greater
than 0.05 Watts/mm.sup.2, greater than 0.1 Watts/mm.sup.2, or
greater than 0.2 Watts/mm.sup.2. However, it should be understood
that the LEDs used in systems and methods presented herein are not
limited to the above-described power and power flux values.
[0113] In some embodiments, the LED may be associated with a
wavelength-converting region. The wavelength-converting region may
be, for example, a phosphor region. The wavelength-converting
region can absorb light emitted by the light generating region of
the LED and emit light having a different wavelength than that
absorbed. In this manner, LEDs can emit light of wavelength(s)
(and, thus, color) that may not be readily obtainable from LEDs
that do not include wavelength-converting regions.
[0114] As used herein, an LED may be an LED die, a partially
packaged LED die, or a fully packaged LED die. It should be
understood that an LED may include two or more LED dies associated
with one another, for example a red-light emitting LED die, a
green-light emitting LED die, a blue-light emitting LED die, a
cyan-light emitting LED die, or a yellow-light emitting LED die.
For example, the two or more associated LED dies may be mounted on
a common package. The two or more LED dies may be associated such
that their respective light emissions may be combined to produce a
desired spectral emission. The two or more LED dies may also be
electrically associated with one another (e.g., connected to a
common ground).
[0115] As used herein, when a structure (e.g., layer, region) is
referred to as being "on", "over" "overlying" or "supported by"
another structure, it can be directly on the structure, or an
intervening structure (e.g., layer, region) also may be present. A
structure that is "directly on" or "in contact with" another
structure means that no intervening structure is present.
[0116] Having thus described several aspects of at least one
embodiment of this invention, it is to be appreciated various
alterations, modifications, and improvements will readily occur to
those skilled in the art. Such alterations, modifications, and
improvements are intended to be part of this disclosure, and are
intended to be within the spirit and scope of the invention.
Accordingly, the foregoing description and drawings are by way of
example only.
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