WO2009016563A1 - Réflecteur et dispositif de sortie de lumière - Google Patents

Réflecteur et dispositif de sortie de lumière Download PDF

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Publication number
WO2009016563A1
WO2009016563A1 PCT/IB2008/052988 IB2008052988W WO2009016563A1 WO 2009016563 A1 WO2009016563 A1 WO 2009016563A1 IB 2008052988 W IB2008052988 W IB 2008052988W WO 2009016563 A1 WO2009016563 A1 WO 2009016563A1
Authority
WO
WIPO (PCT)
Prior art keywords
reflector
infrared
layer
substrate
light
Prior art date
Application number
PCT/IB2008/052988
Other languages
English (en)
Inventor
Leendert Van Der Tempel
Petrus A. J. Holten
Original Assignee
Koninklijke Philips Electronics N.V.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Koninklijke Philips Electronics N.V. filed Critical Koninklijke Philips Electronics N.V.
Publication of WO2009016563A1 publication Critical patent/WO2009016563A1/fr

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21—LIGHTING
    • F21V—FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
    • F21V7/00—Reflectors for light sources
    • F21V7/22—Reflectors for light sources characterised by materials, surface treatments or coatings, e.g. dichroic reflectors
    • F21V7/24—Reflectors for light sources characterised by materials, surface treatments or coatings, e.g. dichroic reflectors characterised by the material
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21—LIGHTING
    • F21V—FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
    • F21V7/00—Reflectors for light sources
    • F21V7/22—Reflectors for light sources characterised by materials, surface treatments or coatings, e.g. dichroic reflectors
    • F21V7/28—Reflectors for light sources characterised by materials, surface treatments or coatings, e.g. dichroic reflectors characterised by coatings
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21—LIGHTING
    • F21Y—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES F21K, F21L, F21S and F21V, RELATING TO THE FORM OR THE KIND OF THE LIGHT SOURCES OR OF THE COLOUR OF THE LIGHT EMITTED
    • F21Y2115/00—Light-generating elements of semiconductor light sources
    • F21Y2115/10—Light-emitting diodes [LED]
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/08—Mirrors

Definitions

  • the present invention relates to a reflector and a light output device comprising such a reflector.
  • light sources like TL fluorescent lamps or light emitting diodes (LEDs) are arranged in metal reflectors serving to direct and/or shape light emitted from the light source.
  • metal reflectors generally reflect both visible and infrared radiation, and thus emit little thermal radiation.
  • power LEDs are too small to be completely cooled by natural convection via the surrounding or ambient air. Therefore, in such an LED lighting device, a large heat sink is usually attached to the LEDs in order to dissipate heat generated during operation from the LEDs to avoid overheating and device degradation. This makes the luminaire both large and heavy as well as costly. Also, when the luminaire is arranged in a ceiling or the like, the ceiling temperature and thermal isolation may affect the heat sink performance.
  • higher ceiling temperature means higher heat sink temperature, which in turn means that less heat or thermal energy can be transferred from the LEDs.
  • the convective heat transfer coefficient becomes lower, demanding an even bigger heat sink. This is because the natural convective heat transfer coefficient scales with ( ⁇ T/L) ⁇ where T is temperature and L is a typical length scale or dimension.
  • a reflector comprising: a reflective member; and a substantially transparent, infrared-emissive layer provided over the reflective member and adapted to transmit visible radiation reflected by the reflective member and emit infrared radiation.
  • the invention is based on the understanding that by providing such a layer over the reflective member, heat may now be removed from the reflector by emission since the superimposed substantially transparent layer is infrared-emissive and therefore may emit thermal radiation in the infrared spectrum. At the same time, incoming light may still be reflected by the reflective member since the superimposed infrared-emissive layer is substantially transparent for visible radiation and therefore passes the visible light.
  • the reflector is thermally emissive, but yet reflective for visible radiation, and acts as cooling means when it is hotter than the ambient. There is therefore no or less need of heat sinks or the like, which provides for a thinner, lighter and/or cheaper device in which the present reflector is included. Also, since heat is removed via infrared- emission, the heat removal performance is less dependent on surrounding temperature (e.g. ceiling temperature). Also, the heat removal capability of the present reflector using infrared- emission is almost proportional to the reflector size, which means that upsizing of a device including the present reflector does not require that the reflector is upsized even more like the conventional heat sink. It should be noted that for reflector temperatures of about 340K, the peak wavelength in Planck's blackbody curve is about S 1 A ⁇ m according to Wien's displacement law, so the emitted radiation is infrared.
  • the substantially transparent, infrared-emissive layer could be transparent, somewhat translucent, semi-transparent, or the like. Transparent is preferred, since it allows specular reflection, while a translucent layer will diffuse the light.
  • the substantially transparent, infrared-emissive layer preferably comprises glass or glass ceramic (glass is usually transparent) or transparent polymer, preferably with 1/aiR ⁇ layer thickness « 1/avis, where a is the absorption coefficient, which is the inverse of the mean free path.
  • the thickness of a polycarbonate layer should be between about 100 ⁇ m and 1 cm, while the thickness of a silicate glass layer should be no less than about 5 ⁇ m and the thickness of a vitreous silica layer should be less than about 0.1 m (depending on purity).
  • absorptivity equals emissivity (Kirchoff s law of thermal radiation), so that an object with high absorption of electromagnetic radiation will also emit more electromagnetic radiation, for example.
  • the above layers may therefore absorb little visible radiation (so that light can pass), but emit more infrared radiation (i.e. heat removal from the reflector).
  • the reflector may further comprise a second infrared-emissive layer arranged on an opposite side of the reflective member compared to the substantially transparent, infrared-emissive layer, e.g. on the backside of the reflector.
  • the second infrared-emissive layer increases the thermal emission and heat removal capability of the reflector.
  • the second infrared-emissive layer may be similar to the first one, but it does not have to be transparent since it is placed on the backside of the reflector.
  • the reflective member may be a surface of, or a layer on, a heat- conducting substrate also comprised in the reflector. Such a reflector may beneficially be used to conduct heat away from one or more light sources in a light output device application.
  • the reflective member is a reflective layer provided over an infrared-emissive substrate, and the substantially transparent, infrared-emissive layer is omitted.
  • Left is a reflector comprising an infrared- emissive substrate provided with a layer adapted to reflect visible radiation. Thus, incoming visible light may be reflected by the reflective layer, while heat may be removed from the reflector by emission by means of the underlying substrate.
  • the reflective layer may for instance be a thin metal no thicker than about 30 nm (depending on the metal). Such a thin metal will also transmit infrared radiation. Thereby, some of the infrared emission may beneficially go through the thin metal layer.
  • the underlying infrared-emissive substrate may be similar to the above substantially transparent, infrared-emissive layer, but it does not have to be transparent since the visible radiation does not pass it. Further, the infrared-emissive substrate may also be heat-conducting.
  • the heat- conducting and infrared-emissive substrate may for instance be a black anodized metal substrate. Such a reflector may beneficially be used to conduct heat away from one or more light sources in a light output device application.
  • a light output device comprising: a reflector according to the above description; and at least one light source.
  • This second aspect exhibits similar advantages as the first aspect of the present invention. For example, since the reflector is thermally emissive, there is no or less need of heat sinks or the like, when the surface of the reflector is sufficiently large and heat generated by the light source(s) is conducted to the reflector.
  • the at least one light source when the reflector itself is heat-conducting, is arranged so that during operation light from the light source(s) is reflected by the reflective member and heat generated by the light source(s) is conducted away from the light source(s) by the heat-conducting substrate and emitted by the infrared-emissive layer(s) or substrate.
  • the light source(s) may for instance be attached or otherwise thermally linked to the reflector.
  • a separate thermal conductor thermally connecting the reflector and light source(s) is envisaged.
  • the present light output device is especially advantageous in case the at least one light source is one or more light emitting diodes (LEDs) or other small light sources like laser diodes, since such light sources are usually too small and powerful to be cooled enough by natural convection via the surrounding air (still the present light output system benefits from such natural cooling in addition to the thermally emissive reflector).
  • the light source could also be lamps used in HID (High Intensity Discharge) lighting, e.g. Philips Arenavision.
  • the at least one LED is arranged in a reflective box in the reflector, the box having a remote phosphor exit window.
  • the phosphor serves to convert at least a portion of the light emitted by the LED(s) to light of a different wavelength. For instance, a portion of blue light emitted by the LED(s) may be converted to yellow light, and unconverted blue light and converted yellow light is then mixed to white light.
  • the present reflector allows feasible cooling in such a device.
  • Apps of the present reflector and light output device include various lighting and illumination applications.
  • Fig. 1 is a schematic cross-sectional side view of a light output device comprising a thermally emitting reflector according to an embodiment of the invention.
  • Fig. 2 is a schematic cross-sectional side view of a light output device comprising a thermally emitting reflector according to another embodiment of the invention.
  • Fig. 3 is a schematic cross-sectional side view of a light output device comprising a thermally emitting reflector according to yet another embodiment of the invention.
  • Fig. 1 is a schematic cross-sectional side view of a light output device 10 comprising a thermally emitting reflector 12 according to an embodiment of the invention.
  • the reflector 12 may have a general flat or concave shape or any other reflector shape as appreciated by the skilled person. Further, an output aperture 14 of the reflector 12 may be rectangular, square, circular, etc.
  • the reflector 12 is a multilayer optical stack comprising a heat-conducting substrate 16 with a front surface 18 reflective for, at least, visual radiation (VIS) and a layer 20 emissive for infrared (thermal) radiation (IR) and transparent for visible radiation.
  • VIS visual radiation
  • IR infrared radiation
  • the substrate 16 may be made of metal, and the reflective front surface 18 may be a surface of the metal substrate (fig. 1). Alternatively, a reflective interface or a separate reflective layer like a mirror coating or multilayer mirror could be provided on the substrate 16 as a reflective member.
  • the transparent IR-emissive layer 20 is provided over the VIS-reflective surface 18 of the substrate 16. Transparent means that it transmits light so that underlying objects are seen clearly, thereby allowing specular reflection.
  • the layer 20 is preferably in optical contact with the substrate 16 to avoid interference reflection losses.
  • the layer 20 is in thermal contact with the substrate 16, which can be direct contact or a sufficiently thin (preferably ⁇ 50 ⁇ m) air gap.
  • the layer 20 covers substantially the entire front side of the substrate 16, for maximized cooling, but could alternatively cover only a portion of the substrate 16.
  • the substrate 16 and/or layer 20 may be tiled or partitioned, e.g. for accommodating thermal expansion and volume shrinkage differences.
  • the layer 20 has a low absorption coefficient for visible radiation, and a high absorption coefficient for infrared radiation.
  • the layer 20 is preferably made of transparent glass or glass ceramic or polymer, like polycarbonate having a thickness between about 100 ⁇ m - 1 cm.
  • the layer 20 could be a sheet, plate, foil, sputtered coating, vapor deposited coating, lacquer, or the like.
  • a layer 20 of glass may be sputtered onto the substrate 16, while a layer 20 of transparent polymer layer may be a 2P layer coating.
  • the transparent IR-emissive layer 20 is the top (effective) layer of the reflector 12.
  • the stack of the reflector 12 may optionally comprise a second IR-emissive layer 22 provided on the backside of the substrate 16, for increased cooling.
  • the second IR- emissive layer 22 may be similar to the layer 20, but it does not have to be transparent since it is placed on the backside of the reflector 12.
  • the light output device further comprises a light emitting diode (LED) 24 attached to the reflector 12, namely to the front of the substrate 16. Means for operating the LED 24 are not shown.
  • LED light emitting diode
  • the LED 24 When the LED 24 is in operation, it emits visible light (VIS). At the same time, it generates heat. At least a portion of the generated heat is transferred to the substrate 16 to which the LED 24 is attached via thermal conduction, and is further spread within the substrate 16.
  • the IR-emission from the substrate 16 itself is however low, since the substrate 16 generally is made of reflective metal. Instead, the heat is transferred via conduction to the superimposed transparent layer 20 (and second layer 22), and from the layer 20 (22) the heat is removed via IR-emission (as well as some natural convection) since the layer 20 (22) contrary to the (metal) substrate 16 is more IR-emissive, whereby increased cooling of the light output device 10 is achieved.
  • the light from the LED 24 incident on the reflector 12 will pass the layer 20 virtually unaffected (due to the transparency/low visible radiation absorption of the layer 20) and be reflected by the reflective surface 18 of the substrate 16 like in a conventional reflector. Consequently, the layer 20 used for IR-emission does not significantly compromise the reflective capability of the reflector 12.
  • Fig. 2 is a schematic cross-sectional side view of a light output device 30 comprising a thermally emitting reflector 32 according to another embodiment of the invention.
  • the reflector 32 may have a general flat or concave shape or any other reflector shape as appreciated by the skilled person. Further, an output aperture 34 of the reflector 32 may be rectangular, square, circular, etc.
  • the reflector 32 is a multilayer optical stack comprising a substrate 36 with a VI S -reflective and IR-transmissive thin metal layer 38 applied thereover.
  • the substrate 36 is preferably heat-conducting and may be made of metal or conductive ceramics, for example.
  • the substrate 36 is also IR-emissive.
  • the substrate may be anodized black (e.g. black anodization (not shown in figure) on aluminum).
  • the superimposed thin metal 38 is a coating or the like no thicker than about 30 nm (depending on the metal). Such a thin metal 38 is able to reflect a visible radiation (light) and transmit infrared (thermal) radiation.
  • the thin metal 38 is preferably in optical contact with the underlying substrate 36 to avoid interference reflection losses. Also preferably, the thin metal 38 is in direct contact with the substrate 36. Also preferably, the thin metal 38 covers substantially the entire front side of the substrate 36, for maximized reflection, but could alternatively cover only a portion of the substrate 36. In fig. 2, the thin metal 38 is the top (effective) layer of the reflector 32. The thin metal 38 could be protected by NONON (N is silicon nitride and O is silicon oxide) or other (dielectric) stacks and coatings, as appreciated by the skilled person.
  • the light output device further comprises a light emitting diode (LED) 44 attached to the reflector 32, here to the substrate 36. Means for operating the LED 44 are not shown.
  • LED light emitting diode
  • the LED 44 When the LED 44 is in operation, it emits visible light (VIS). At the same time, it generates heat. At least a portion of the generated heat is transferred to the substrate 36 to which the LED 44 is attached via thermal conduction, and is further spread within the substrate 36. The heat is then removed by means of IR-emission from the substrate 36 (as well as some natural convection), whereby increased cooling of the light output device 30 is achieved. Since the thin metal 38 is IR-transmissive, the infrared radiation may be emitted through the thin metal 38. At the same time, the light from the LED 44 incident on the reflector 32 will be reflected by the thin metal 38, to direct and/or shape the light from the LED 44 like a traditional reflector.
  • Fig. 3 is a schematic cross-sectional side view of a light output device 10 comprising a thermally emitting reflector 12 according to yet another embodiment of the invention.
  • the light output device of fig. 3 is similar to that of fig. 1, except in that the LED 24 is arranged in a reflective box 26 having a remote phosphor exit window 28.
  • the LED 24 is thermally linked to the reflector 12, e.g. via the box 26 being thermally conductive and attached to (fig. 3) or otherwise thermally linked to the reflector 12.
  • a second IR- emissive layer like the layer 22 in fig. 1 could be deployed.
  • heat generated by the LED 24 is transferred (e.g. via the box 26) to the reflector 12, where it is removed in the same way as explained above in relation to fig. 1.
  • the reflector 12 Upon operation, heat generated by the LED 24 is transferred (e.g. via the box 26) to the reflector 12, where it is removed in the same way as explained above in relation to fig. 1.
  • at least a portion of light from the LED 24 is converted by the exit window 28, and converted light or a mixture of unconverted and converted light (VIS') is then reflected by the reflective surface 18 without significant interference.
  • VIS' unconverted and converted light
  • the present reflector and light output device include various lighting and illumination applications.
  • the person skilled in the art realizes that the present invention by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims.
  • the above light output devices may comprise more than one LED or one or more other light sources.
  • the reflective box and remote phosphor exit window could be applied also to the embodiment shown in fig. 2.
  • optics may be placed in front of the reflector, for instance PMMA microprisms or microlenses.
  • the above surfaces, layers and substrates could be of single- or multi-layer or stack type, as appreciated by the skilled person.
  • the present light output device could include more than one of the present reflectors.

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Arrangement Of Elements, Cooling, Sealing, Or The Like Of Lighting Devices (AREA)
  • Non-Portable Lighting Devices Or Systems Thereof (AREA)

Abstract

La présente invention porte sur un réflecteur (12 ; 32), comprenant : un élément réfléchissant (18 ; 38) ; et une couche d'émission infrarouge sensiblement transparente (20) disposée sur l'élément réfléchissant et apte à transmettre un rayonnement visible réfléchi par l'élément réfléchissant et à émettre un rayonnement infrarouge. Le réflecteur peut ainsi servir de moyen de refroidissement. La présente invention porte également sur un dispositif de sortie de lumière (10 ; 30) comprenant un tel réflecteur.
PCT/IB2008/052988 2007-08-02 2008-07-25 Réflecteur et dispositif de sortie de lumière WO2009016563A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP07113653 2007-08-02
EP07113653.5 2007-08-02

Publications (1)

Publication Number Publication Date
WO2009016563A1 true WO2009016563A1 (fr) 2009-02-05

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PCT/IB2008/052988 WO2009016563A1 (fr) 2007-08-02 2008-07-25 Réflecteur et dispositif de sortie de lumière

Country Status (2)

Country Link
TW (1) TW200936955A (fr)
WO (1) WO2009016563A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8632204B2 (en) 2009-06-25 2014-01-21 Koninklijke Philips N.V. Solar powered lighting arrangement

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA3095743A1 (fr) * 2018-04-16 2019-10-24 Romy M. FAIN Procedes de fabrication, structures et utilisations pour refroidissement radiatif passif
DE102020128337A1 (de) * 2020-10-28 2022-04-28 Heraeus Noblelight Gmbh Strahlerbauteil mit einer Reflektorschicht sowie Verfahren für seine Herstellung

Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6484506A (en) * 1987-09-25 1989-03-29 Toshiba Electric Equip Reflector
JPS6490401A (en) * 1987-10-01 1989-04-06 Kitazawa Maruchikooto Kk Endothermic reflecting mirror
JPH01187703A (ja) * 1988-01-21 1989-07-27 Toshiba Corp 反射鏡
JPH03225702A (ja) * 1990-01-29 1991-10-04 Toshiba Lighting & Technol Corp 照明器具
JPH10199489A (ja) * 1990-08-07 1998-07-31 Toshiba Lighting & Technol Corp 反射鏡付電球
EP1081771A2 (fr) * 1999-09-03 2001-03-07 Hewlett-Packard Company Dispositif émetteur de lumière
US6670045B1 (en) * 1997-11-19 2003-12-30 Alcan Technology & Management Ltd. Reflector with a resistant surface
JP2004170877A (ja) * 2002-11-22 2004-06-17 Sharp Corp 反射体及びその製造方法
CN1614297A (zh) * 2003-11-04 2005-05-11 廖海 红外线光源探照灯
US20060147673A1 (en) * 2003-02-25 2006-07-06 Kohei Ueda Precoated metal plate for reflection plate
EP1742088A1 (fr) * 2004-04-28 2007-01-10 Nippon Steel Corporation Plaque de réflexion de rayon visible et dispositif électrique/électronique utilisant cette dernière

Patent Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6484506A (en) * 1987-09-25 1989-03-29 Toshiba Electric Equip Reflector
JPS6490401A (en) * 1987-10-01 1989-04-06 Kitazawa Maruchikooto Kk Endothermic reflecting mirror
JPH01187703A (ja) * 1988-01-21 1989-07-27 Toshiba Corp 反射鏡
JPH03225702A (ja) * 1990-01-29 1991-10-04 Toshiba Lighting & Technol Corp 照明器具
JPH10199489A (ja) * 1990-08-07 1998-07-31 Toshiba Lighting & Technol Corp 反射鏡付電球
US6670045B1 (en) * 1997-11-19 2003-12-30 Alcan Technology & Management Ltd. Reflector with a resistant surface
EP1081771A2 (fr) * 1999-09-03 2001-03-07 Hewlett-Packard Company Dispositif émetteur de lumière
JP2004170877A (ja) * 2002-11-22 2004-06-17 Sharp Corp 反射体及びその製造方法
US20060147673A1 (en) * 2003-02-25 2006-07-06 Kohei Ueda Precoated metal plate for reflection plate
CN1614297A (zh) * 2003-11-04 2005-05-11 廖海 红外线光源探照灯
EP1742088A1 (fr) * 2004-04-28 2007-01-10 Nippon Steel Corporation Plaque de réflexion de rayon visible et dispositif électrique/électronique utilisant cette dernière

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8632204B2 (en) 2009-06-25 2014-01-21 Koninklijke Philips N.V. Solar powered lighting arrangement
US9562659B2 (en) 2009-06-25 2017-02-07 Philips Lighting Holding B.V. Solar-powered lighting arrangement

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