THERMAL MANAGEMENT SYSTEMS FOR LIGHT EMITTING DEVICES AND SYSTEMS

- Luminus Devices, Inc.

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.

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Description

RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §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

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

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

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.

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).

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

Light emitting devices, and related components, systems, and methods associated therewith are provided. Related components and/or systems can include thermal management systems.

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.

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.

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.

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

FIG. 1a is a schematic drawing of a light emitting system according to one embodiment;

FIG. 1b is a schematic drawing of a light emitting system according to one embodiment;

FIG. 2 is a schematic drawing of a side-view of a light emitting system according to one embodiment;

FIG. 3 is a schematic drawing of a top-view of the light emitting system of FIG. 2 according to one embodiment;

FIG. 4 is a schematic drawing of a top-view of part of a light emitting system according to one embodiment;

FIG. 5 is a schematic drawing of a top-view of a light emitting system according to one embodiment;

FIG. 6 is a schematic drawing of a side-view of a light emitting system according to one embodiment;

FIG. 7 is a schematic drawing of a side-view of a light emitting system according to one embodiment;

FIG. 8 is a schematic drawing of a side-view of a light emitting system according to one embodiment;

FIG. 9 is a schematic drawing of a top-view of part of the light emitting system of FIG. 8 according to one embodiment;

FIG. 10 is a schematic drawing of a side-view a light emitting system according to one embodiment;

FIG. 11 is a schematic drawing of a bottom-view of part of the light emitting system of FIG. 10 according to one embodiment;

FIG. 12 is a schematic drawing of a perspective-view of the light emitting system of FIG. 10 according to one embodiment;

FIG. 13 is a schematic drawing of a heat spreading component according to one embodiment;

FIG. 14 is a schematic drawing of a side-view a light emitting system according to one embodiment;

FIG. 15 is a schematic drawing of a side-view of part of a light emitting system according to one embodiment;

FIG. 16 is a schematic drawing of a side-view of part of a light emitting system according to one embodiment;

FIG. 17 is a schematic drawing of a perspective-view of part of the light emitting system of FIG. 16 according to one embodiment;

FIG. 18 is a schematic drawing of a side-view of a light emitting system according to one embodiment;

FIG. 19 is a schematic drawing of a side-view of a light emitting system according to one embodiment;

FIG. 20 is a schematic drawing of a side-view of a light emitting system according to one embodiment;

FIG. 21 is a schematic drawing of a side-view of a light emitting system according to one embodiment;

FIG. 22 is a schematic drawing of a side-view of a light emitting system according to one embodiment;

FIG. 23 is a schematic drawing of a perspective-view of a display system according to one embodiment;

FIG. 24 is a schematic drawing of a back-view of a display system according to one embodiment;

FIG. 25 is a schematic drawing of a light emitting die according to one embodiment.

DETAILED DESCRIPTION

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).

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.

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).

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.

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).

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° C.

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.

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.

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).

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.

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.

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.

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).

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.

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.

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.

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.

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.

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 (θ) with respect to a horizontal side 118 of the illumination panel 110. The angle θ 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° (e.g., greater than about 10°, greater than about 20°, greater than about 30°, greater than about 40°, greater than about 50°, greater than about 60°). In some embodiments, the mount 142 is arranged to lie parallel to a vertical side 119 of the illumination panel 110.

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 (θ) 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.

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.

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.

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.

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).

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.

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).

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.

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.

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.

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%).

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.

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.

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.

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.

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.

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.

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.

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).

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).

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).

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.

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.

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.

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.

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.

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° angle) with respect to the input sides of the wedge optics.

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%).

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.

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° to a surface normal of some or all of the heat pipes and/or vapor plates (e.g., greater than about 40°, greater than about 60°, greater than about 80°).

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.

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.

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.

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.

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.

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.

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.

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).

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.

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).

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).

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).

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.

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.

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.

Light emitting devices (e.g., devices 130) of embodiments presented may include light emitting diodes and/or laser diodes.

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.

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.

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.

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, (2×2) 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.

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.

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.

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.

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).

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.

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/mm2, greater than 0.05 Watts/mm2, greater than 0.1 Watts/mm2, or greater than 0.2 Watts/mm2. 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.

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.

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).

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.

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.

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.

Patent History

Publication number: 20110121703
Type: Application
Filed: Feb 22, 2008
Publication Date: May 26, 2011
Applicant: Luminus Devices, Inc. (Billerica, MA)
Inventors: Robert F. Karlicek, JR. (Chelmsford, MA), Daniel Yen Chu (Andover, MA), Joseph D. Whitney (Merrimack, NH), Paul Panaccione (Newburyport, MA), Warren P. Pumyea (Gardner, MA), Brian L. Stoffers (Billerica, MA), Michael A. Joffe (Harvard, MA), Alexei A. Erchak (Cambridge, MA)
Application Number: 12/036,058

Classifications

Current U.S. Class: Having Heat Conducting Path (313/46); Assembling Or Joining (29/428)
International Classification: H01J 61/52 (20060101); B23P 11/00 (20060101);