Patent Publication Number: US-9423084-B2

Title: Indirect lighting apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is the National Stage of International Application No. PCT/KR2012/010112, filed on Nov. 27, 2012, and claims priority from and the benefit of Korean Patent Application No. 10-2011-0127545, filed on Dec. 1, 2011, which are hereby incorporated by reference for all purposes as if fully set forth herein. 
     BACKGROUND 
     1. Field 
     The present invention relates to a lighting apparatus using a semiconductor light emitting device as a light source and, more particularly, to an indirect lighting apparatus. 
     2. Discussion of the Background 
     Semiconductor light emitting devices are used for various purposes and have been spotlighted as a light source of a lighting apparatus, due to various advantages thereof, such as rapid response, high energy efficiency, long lifespan, and the like. 
     A lighting apparatus employing a semiconductor light emitting device typically includes a light emitting diode and phosphors, and realizes white light through combination of colors. For example, white light can be realized by a combination of a blue light emitting diode and yellow phosphors. 
     In such a general white lighting apparatus, light emitted from a light emitting diode and light subjected to wavelength conversion by phosphors are used for direct lighting. Such a direct lighting apparatus allows light emitted from the light emitting diode and having relatively high intensity to enter the eyes of a user, thereby providing undesirable effects to the user. 
     In the white lighting apparatus, the semiconductor light emitting device is generally used to emit white light by coating or depositing phosphors onto a light emitting diode chip. However, such a white semiconductor light emitting device is likely to suffer from light loss due to re-entering of light into the light emitting diode chip after being subjected to wavelength conversion by the phosphors. 
     SUMMARY 
     The present invention is aimed at providing a lighting apparatus capable of protecting a user, particularly, the eyes of a user. 
     The present invention is aimed at providing a lighting apparatus capable of reducing light loss due to a light emitting diode chip. 
     The present invention provides an indirect lighting apparatus. The indirect lighting apparatus includes: a semiconductor light emitting device; a reflector disposed above the semiconductor light emitting device reflector; and a wavelength conversion layer formed on a surface of the reflector and separated from the semiconductor light emitting device. The wavelength conversion layer contains phosphors excited by light emitted from the semiconductor light emitting device and emitting light subjected to wavelength conversion, and the reflector reflects the light received from the wavelength conversion layer towards the wavelength conversion layer. 
     As used herein, the term “indirect lighting apparatus” is compared with a direct lighting apparatus which is designed to use light directly emitted from a light source such as a semiconductor light emitting device, and means a lighting apparatus designed to reflect light emitted from a light source towards surroundings such that the reflected light can be used for illumination. The indirect lighting apparatus can protect a user by preventing direct exposure of the user to light emitted from the semiconductor light emitting device. 
     The indirect lighting apparatus may further include a lower filter disposed under the semiconductor light emitting device and filtering light directed to the outside of the indirect lighting apparatus. The lower filter can reflect UV light while allowing transmission of visible light therethrough. For example, the semiconductor light emitting device may include a UV light emitting diode chip. In this case, the lower filter prevents UV light from being emitted to the outside of the indirect lighting apparatus. 
     The indirect lighting apparatus may further include a diffusing plate disposed below the semiconductor light emitting device. The diffusing plate can mix light emitted from the semiconductor light emitting device with light subjected to wavelength conversion in the wavelength conversion layer by diffusing the light. 
     The diffusing plate may have a roughness pattern formed on a surface thereof. The roughness pattern may be adopted for extraction of light or for scattering of light. 
     The wavelength conversion layer may include phosphors emitting different colors, for example, first phosphors and second phosphors. 
     The phosphors may be mixed with each other, but are not limited thereto. Alternatively, the phosphors may be separated from each other. For example, the wavelength conversion layer may include first phosphor concentrated regions and second phosphor concentrated regions. Alternatively, the wavelength conversion layer may include a first wavelength conversion layer containing first phosphors and a second wavelength conversion layer containing second phosphors. In addition, a band pass filter may be disposed between the first wavelength conversion layer and the second wavelength conversion layer. 
     In some embodiments, the wavelength conversion layer may be disposed restrictively on some surface region of the reflector. For example, the wavelength conversion layer may be disposed within a beam angle range of the semiconductor light emitting device. In addition, the semiconductor light emitting device may include a semiconductor light emitting diode chip and a phosphor coating layer formed on a side surface of the semiconductor light emitting diode chip. 
     The semiconductor light emitting device is mounted on a printed circuit board. Here, the printed circuit board is disposed to face the reflector and the semiconductor light emitting device is disposed between the printed circuit board and the reflector. 
     In addition, a plurality of semiconductor light emitting devices may be mounted on the printed circuit board. 
     The reflector may have a concave reflective face, like an inner wall of a hemispherical or a hemiellipsoid body, without being limited thereto. Alternatively, the reflector may have an inner wall shape of a hemicylinder. 
     For example, the printed circuit board may have an elongated shape, the plurality of semiconductor light emitting devices may be arranged in a longitudinal direction of the printed circuit board, and the reflector may have an elongated shape and be disposed above the printed circuit board. 
     In some embodiments, the printed circuit board may be a light transmitting substrate. Thus, light emitted from the semiconductor light emitting device can pass through the printed circuit board. 
     The indirect lighting apparatus may further include a second wavelength conversion layer disposed under the printed circuit board and converting wavelengths of light passing through the second wavelength conversion layer. 
     The indirect lighting apparatus may further include a band pass filter disposed between the printed circuit board and the second wavelength conversion layer to reflect light subjected to wavelength conversion in the second wavelength conversion layer while allowing transmission of light emitted from the semiconductor light emitting device therethrough. 
     In some embodiments, light emitted from semiconductor light emitting device can be directly incident on the reflector. In other embodiments, light emitted from the semiconductor light emitting device may enter a light guide plate such that light emitted from the light guide plate is incident on the reflector. 
     According to embodiments of the present invention, indirect lighting is adopted to reduce bad effects of light emitted from the semiconductor light emitting device on human bodies. Furthermore, a wavelength conversion layer is disposed on a reflector to reduce light loss by preventing light subjected to wavelength conversion from re-entering the light emitting diode chip. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic perspective view of a lighting apparatus in accordance with one embodiment of the present invention. 
         FIG. 2  is a cross-sectional view of the lighting apparatus taken along line A-A of  FIG. 1 . 
         FIG. 3  to  FIG. 8  are cross-sectional views of lighting apparatuses in accordance with other embodiments of the present invention. 
         FIG. 9  is a side sectional view of a lighting apparatus in accordance with yet another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS 
     Hereinafter, embodiments of the present invention will be described in more detail with reference to the accompanying drawings. It should be understood that the following embodiments are given by way of illustration only to provide a thorough understanding of the invention to those skilled in the art. Therefore, the present invention is not limited to the following embodiments and may be embodied in different ways. Further, the widths, lengths, and thicknesses of certain elements, layers or features may be exaggerated for clarity. Like components will be denoted by like reference numerals throughout the specification. 
       FIG. 1  is a schematic perspective view of a lighting apparatus  10  in accordance with one embodiment of the present invention, and  FIG. 2  is a cross-sectional view of the lighting apparatus taken along line A-A of  FIG. 1 . 
     Referring to  FIGS. 1 and 2 , the indirect lighting apparatus  10  includes a reflector  21 , a wavelength conversion layer  23 , a lower filter  25 , a diffusing plate  27 , a printed circuit board  31 , and a semiconductor light emitting device  33 . 
     The printed circuit board  31  has circuits for supplying electric current to the semiconductor light emitting devices. The printed circuit board  31  may have an elongated shape in one direction (longitudinal direction), as shown in  FIG. 1 . 
     The semiconductor light emitting device  33  is mounted on the printed circuit board  31 . A plurality of semiconductor light emitting devices  33  may be arranged on the printed circuit board  31  in the longitudinal direction thereof. Here, the semiconductor light emitting devices  33  may be packaged light emitting diode chips, without being limited thereto. Alternatively, the semiconductor light emitting devices  33  may be light emitting diode chips. 
     The semiconductor light emitting devices  33  include gallium nitride-based light emitting diode chips and may emit UV light or blue light. In addition, an AlGaInP or AlGaInAs-based green or red light emitting diode chip may be additionally mounted on the printed circuit board  31 . 
     The reflector  21  is disposed above the semiconductor light emitting devices  33 . The semiconductor light emitting devices  33  are disposed between the printed circuit board  31  and the reflector  21  to emit light towards the reflector  21 . The reflector  21  may have a reflective face, which is concave in one direction, like an inner wall of a cylinder, and extends in the longitudinal direction of the printed circuit board  31 , as shown in  FIG. 1 . The reflector  21  is disposed above the printed circuit board  31  and reflects light emitted from the semiconductor light emitting devices  33 . 
     The reflector  21  may be prepared by forming a metal plate such as an aluminum plate, without being limited thereto. Alternatively, the reflector  21  may be prepared by coating a reflective layer onto a metal or plastic molded article. The reflective layer may be formed of any material capable of reflecting light emitted from the semiconductor light emitting devices  33  and the wavelength conversion layer  23 . 
     The wavelength conversion layer  23  is provided to a surface of the reflector  21 . Accordingly, the wavelength conversion layer  23  is separated from the semiconductor light emitting devices  33 . The wavelength conversion layer  23  may contain phosphors excited by light emitted from the semiconductor light emitting devices  33  and emitting light having a long wavelength. Furthermore, the wavelength conversion layer  23  may contain plural kinds of phosphors emitting different colors. 
     The lower filter  25  is disposed under the semiconductor light emitting devices  33  and filters light directed to the outside of the indirect lighting apparatus  10 . For example, the lower filter  25  reflects UV light while allowing transmission of visible light therethrough. Accordingly, when the semiconductor light emitting devices  33  include a UV light emitting diode chip to emit UV light, it is possible to prevent UV light, which is not subjected to wavelength conversion by the wavelength conversion layer  23 , from being emitted outside the indirect lighting apparatus  10 . 
     The diffusing plate  27  is disposed below the semiconductor light emitting devices  33 , for example, under the lower filter  25 . The diffusing plate  27  mixes light emitted outside the indirect lighting apparatus  10  by diffusing the light. Further, the diffusing plate  27  may have a roughness pattern  27   a  formed on a light exit face thereof. The roughness pattern  27   a  may be formed to enhance extraction efficiency of light emitted from the diffusing plate  27  or to scatter the light. 
     According to this embodiment, the semiconductor light emitting devices  33  are disposed below a central region of the reflector  21  and light reflected by the reflector  21  is directed towards lower sides of the semiconductor light emitting devices  33 . Here, most light emitted from semiconductor light emitting devices  33  is subjected to wavelength conversion by the phosphors in the wavelength conversion layer  23 , and light emitted from the phosphors is directed in all directions without a particular beam orientation. As a result, since the phosphors are separated from the semiconductor light emitting devices  33 , it is possible to reduce light loss due to re-entrance of wavelength-converted light into the semiconductor light emitting devices  33 . 
       FIG. 3  is a cross-sectional view of an indirect lighting apparatus  20  in accordance with another embodiment of the present invention. 
     Referring to  FIG. 3 , the indirect lighting apparatus  20  according to this embodiment is generally similar to the indirect lighting apparatus  10  of  FIGS. 1 and 2  except that the wavelength conversion layer of the indirect lighting apparatus  20  includes a blue phosphor concentrated region  23 B, a green phosphor concentrated region  23 G, and a red phosphor concentrated region  23 R. 
     Specifically, in this embodiment, the phosphors emitting different colors are separated from each other, instead of being mixed with each other. Such concentrated regions  23 R,  23 G,  23 B may be formed by dotting or screen printing. 
     Thus, it is possible to prevent color spots due to uneven mixing of the phosphors or to prevent formation of defective products due to difference in mixing ratio of the phosphors. 
       FIG. 4  is a cross-sectional view of an indirect lighting apparatus  30  in accordance with a further embodiment of the present invention. 
     Referring to  FIG. 4 , the indirect lighting apparatus  30  according to this embodiment is generally similar to the indirect lighting apparatus  10  of  FIGS. 1 and 2  except that the wavelength conversion layer of the indirect lighting apparatus  30  is composed of a plurality of wavelength conversion layers converting light into different colors. 
     Specifically, in this embodiment, the wavelength conversion layer may include a blue wavelength conversion layer  23 B that emits blue light, a green wavelength conversion layer  23 G that emits green light, and a red wavelength conversion layer  23 R that emits red light, which are stacked one above another. 
     Here, the wavelength conversion layer that emits light having a relatively short wavelength is disposed closer to the reflector  21  than the other wavelength conversion layers. That is, the wavelength conversion layers are stacked in order of the blue wavelength conversion layer  23 B, the green wavelength conversion layer  23 G and the red wavelength conversion layer  23 R from the reflector  21 . With this structure, it is possible to minimize loss of light subjected to wavelength conversion by one wavelength conversion layer due to the other wavelength conversion layers. 
     In this embodiment, the semiconductor light emitting devices  33  may emit UV light. On the other hand, when the semiconductor light emitting devices  33  emit blue light, the blue wavelength conversion layer  23 B can be omitted. 
       FIG. 5  is a cross-sectional view of an indirect lighting apparatus  40  in accordance with yet another embodiment of the present invention. 
     Referring to  FIG. 5 , the indirect lighting apparatus  40  according to this embodiment is generally similar to the indirect lighting apparatus  10  of  FIGS. 1 and 2  except that the wavelength conversion layer of the indirect lighting apparatus  40  is composed of a plurality of wavelength conversion layers  23 B,  23 G,  23 R, which convert light into different colors, and band pass filters  24   a ,  24   b.    
     Specifically, in this embodiment, the wavelength conversion layer may include a blue wavelength conversion layer  23 B that emits blue light, a green wavelength conversion layer  23 G that emits green light, a red wavelength conversion layer  23 R that emits red light, and the band pass filters  24   a ,  24   b  disposed between these wavelength conversion layers. Here, the wavelength conversion layer that emits light having a relatively long wavelength is disposed closer to the reflector  21  than the other wavelength conversion layers. That is, the wavelength conversion layers are stacked in order of the red wavelength conversion layer  23 R, the green wavelength conversion layer  23 G and the blue wavelength conversion layer  23 B from the reflector  21 . 
     On the other hand, a first band pass filter  24   a  is disposed between the blue wavelength conversion layer  23 B and the green wavelength conversion layer  23 G, and a second band pass filter  24   b  is disposed between the green wavelength conversion layer  23 G and the red wavelength conversion layer  23 R. The first band pass filter  24   a  reflects blue light while allowing transmission of green and red light therethrough. In addition, the second band pass filter  24   b  reflects green light while allowing transmission of red light therethrough. Furthermore, when the semiconductor light emitting devices  33  emits UV light, the first and second band pass filters  24   a ,  24   b  allow transmission of UV light therethrough. 
     In this embodiment, the wavelength conversion layer that emits light having a relatively long wavelength is illustrated as being disposed closer to the reflector  21  than the other wavelength conversion layers. However, the wavelength conversion layers may be disposed in reverse order. That is, the wavelength conversion layers are stacked in order of the blue wavelength conversion layer  23 B, the green wavelength conversion layer  23 G and the red wavelength conversion layer  23 R from the reflector  21 . In this case, the first band pass filter  24   a  is disposed between the red wavelength conversion layer  23 R and the green wavelength conversion layer  23 G to reflect red light while allowing transmission of blue and green light therethrough. In addition, the second band pass filter  24   b  is disposed between the green wavelength conversion layer  23 G and the blue wavelength conversion layer  23 B to reflect green light while allowing transmission of blue light therethrough. 
     According to this embodiment, the first and second band pass filters  24   a ,  24   b  are adopted to reflect light, which has been subjected to wavelength conversion, thereby preventing light loss due to absorption of the wavelength converted light into the other kinds of phosphors. 
       FIG. 6  is a cross-sectional view of an indirect lighting apparatus  50  in accordance with yet another embodiment of the present invention. 
     Referring to  FIG. 6 , the indirect lighting apparatus  50  according to this embodiment is generally similar to the indirect lighting apparatus  10  of  FIGS. 1 and 2  except that the wavelength conversion layer  23  is defined on some region of the reflector  21 . 
     That is, in the indirect lighting apparatus  10  of  FIGS. 1 and 2 , the reflector  21  is disposed to reflect any light emitted from side and upper surfaces of the semiconductor light emitting device  23 . However, the semiconductor light emitting devices  33  generally emit most light within a certain beam angle to the outside. 
     Accordingly, in this embodiment, the wavelength conversion layer  23  may be generally disposed within a beam angle range of light emitted from the semiconductor light emitting devices  33 , thereby enabling reduction in amounts of the phosphors. 
     Further, when the semiconductor light emitting devices  33  are light emitting diode chips, a phosphor coating layer  23   a  may be formed on a side surface of each of the light emitting diode chips to prevent direct reflection of light by the reflector  21  after being emitted from the side surface of each of the light emitting diode chips  33 . Such a phosphor coating layer  23   a  may be partially formed on the side surface of the light emitting diode chip by conformal coating. 
       FIG. 7  is a cross-sectional view of an indirect lighting apparatus  60  in accordance with yet another embodiment of the present invention. 
     Referring to  FIG. 7 , the indirect lighting apparatus  60  according to this embodiment is generally similar to the indirect lighting apparatus  10  of  FIGS. 1 and 2  except that two rows of semiconductor light emitting devices  33  are arranged on the printed circuit board  31  in the indirect lighting apparatus  60 . 
     That is, although the semiconductor light emitting devices  33  are arranged in the longitudinal direction of the printed circuit board  31  as shown in  FIG. 1 , the semiconductor light emitting devices  33  are arranged in plural rows. 
     In this embodiment, the plural rows of semiconductor light emitting devices  33  are arranged on a single printed circuit board  31 . However, it should be understood that the present invention is not limited thereto. In other embodiments, a plurality of printed circuit boards  31  each having the semiconductor light emitting devices  33  mounted thereon may be arranged parallel to each other. 
       FIG. 8  is a cross-sectional view of an indirect lighting apparatus  70  in accordance with yet another embodiment of the present invention. 
     Referring to  FIG. 8 , the indirect lighting apparatus  70  according to this embodiment is generally similar to the indirect lighting apparatus  10  of  FIGS. 1 and 2  except that a printed circuit board  51  of the indirect lighting apparatus  70  is a light transmitting substrate. 
     That is, according to this embodiment, the printed circuit board  51  may be fabricated as a light transmitting substrate, such as a glass substrate, a quartz substrate, and the like. In addition, substrates of various light transmitting materials, for example, a resin substrate or a ceramic substrate, may be used as the printed circuit board. A printed circuit may be partially formed on such a substrate of a light transmitting material. 
     The semiconductor light emitting devices  33  are provided in the form of light emitting diode chips and may be attached to an upper surface of a printed circuit board  51  via a light transmitting adhesive. Accordingly, light emitted from the semiconductor light emitting devices  33  can be discharged to the outside through the printed circuit board  51 . 
     A second wavelength conversion layer  55  may be disposed below the printed circuit board  51 . The second wavelength conversion layer  55  is excited by light passing through the printed circuit board  51  such that wavelength-converted light is emitted from the second wavelength conversion layer  55 . The second wavelength conversion layer  55  contains phosphors as in the wavelength conversion layer  23 . 
     A band pass filter  53  may be disposed between the second wavelength conversion layer  55  and the semiconductor light emitting devices  33 . The band pass filter  53  reflects the wavelength-converted light emitted from the second wavelength conversion layer  55  while allowing transmission of light emitted from the semiconductor light emitting devices  33  therethrough. Accordingly, it is possible to prevent light loss by preventing the light subjected to wavelength conversion by the second wavelength conversion layer  55  from re-entering the semiconductor light emitting devices  33 . 
       FIG. 9  is a side sectional view of an indirect lighting apparatus  80  in accordance with yet another embodiment of the present invention. 
     Referring to  FIG. 9 , the indirect lighting apparatus  80  further includes a light guide member  65  unlike the above embodiments. 
     Semiconductor light emitting devices  61  are disposed on side surfaces of the light guide member  65 . The semiconductor light emitting devices  61  may be mounted on a printed circuit board  63 . For example, the semiconductor light emitting devices  61  may be lateral type light emitting diodes, without being limited thereto. The semiconductor light emitting devices  61  emit light towards the side surfaces of the light guide member  65 . On the other hand, the light guide member  65  discharges light towards the reflector  21  after receiving the light from the semiconductor light emitting devices  61 . 
     In this embodiment, the light guide member  65  may have an elongated bar shape and light reflected by the reflector  21  may be discharged downwards through the opposite sides of the light guide member  65 . 
     According to this embodiment, it is possible to provide the lighting apparatus capable of illuminating a wide area using a relatively small number of semiconductor light emitting devices  65  by adopting the light guide member  65 . 
     Although some embodiments have been described above, it should be understood that some features of a certain embodiment may also be applied to other embodiments without departing from the spirit and scope of the invention. In addition, it should be understood that the present invention is not limited to the embodiments described above, and that various modifications, variations, and alterations can be made without departing from the spirit and scope of the invention.