Abstract:
A bulb-type lighting source employs a light-emitting element in a structure that facilitates heat dispersal. The lighting source includes a first heat sink member mounted in a bowl shaped case supporting a power supply circuit. A mounting substrate is positioned in surface contact with a surface of the heat sink member and is capable of supporting a light-emitting unit. A globe covers the light-emitting unit to permit light emission. A second heat sink member has a surface in contact with a perimeter of the mounting substrate and offset from the light-emitting unit to provide a second part in surface contact with the first heat member to facilitate the release of heat.

Description:
TECHNICAL FIELD 
     The present invention relates to a bulb-type lighting source that uses a light-emitting element such as an LED, and in particular to a technology for more effective heat dispersal from the light-emitting element. 
     Background Art 
     In recent years, research and development of technologies that employ light-emitting elements such as LEDs in lamps has progressed in the lighting field (see Patent Literature 1), and so bulb-type lighting sources that are alternatives to incandescent light bulbs have come under consideration (see Patent Literature 2 and 3). A bulb-type lighting source is sought that is restricted to external dimensions matching those of incandescent light bulbs for considerations of compatibility with lighting equipment, and also that can produce a total luminous flux suitable for use in lighting applications. 
     To produce a total luminous flux suitable for use in lighting applications, a rather high electrical power input must be applied to LEDs. As it happens, as electrical power input to an LED increases, so too does heat generated by the LED, thus leading to a rise in temperature. In an LED, high temperatures are accompanied by a drop in luminous efficacy. Therefore, the expected total luminous flux cannot be obtained through a simple increase in electrical power input. For this reason, standard practice is to place a large-volume heat sink member at the surface opposite the LED mounting surface of the LED mounting substrate (i.e. the bottom surface) in order to enhance the heat dispersal characteristics of the LED. 
     Citation List 
     Patent Literature 
     
         
         [Patent Literature 1] 
       
    
     Japanese Patent Application Publication No. 2005-038798
     [Patent Literature 2]   

     Japanese Patent Application Publication No. 2003-124528
     [Patent Literature 3]   

     Japanese Patent Application Publication No. 2004-265619
     [Patent Literature 4]   

     Japanese Patent Application Publication No. 2005-294292 
     SUMMARY OF INVENTION 
     Technical Problem 
     Thus far, lamps that employ light-emitting elements such as LEDs have rarely assumed a structure with a sealed mounting substrate, and have obtained a heat dispersal effect by relying on natural cooling of the mounting substrate and of the heat sink member at the bottom surface of the mounting substrate. 
     However, in a bulb-shaped lighting source, a protective cover (globe) is required to cover the mounting substrate in order to allow use in ordinary domestic light fixtures. Thus, a heat dispersal effect through natural cooling cannot very well be expected. Also, as mentioned above, there is a limit on the volume of the heat sink member at the bottom surface of the mounting substrate because the external dimensions of bulb-shaped lighting sources are restricted. If a bulb-shaped lighting source is to use light-emitting elements such as LEDs in this way, the heat dispersal structure must be taken into consideration due to such various limitations. 
     The present invention has been achieved in view of the above problems, and an aim thereof is to provide a bulb-type lighting source that employs a light-emitting element and that has better heat dispersal characteristics than the conventional technology. 
     Solution to Problem 
     In order to solve the above problems, the present invention provides a bulb-type lighting source that receives electric power supplied via a base, comprising: a bowl-shaped case which accommodates a power supply circuit in an inner space thereof and to which the base is attached, a first heat sink member that closes a mouth of the bowl-shaped case, a mounting substrate that is in surface contact with a front surface of the first heat sink member opposite a rear surface of the first heat sink member that faces the inner space of the bowl-shaped case, a light-emitting unit that is mounted on a front surface of the mounting substrate opposite a rear surface of the mounting substrate which is in surface contact with the first heat sink member and that includes (i) a light-emitting element that emits light upon receiving electric power supplied by the power supply circuit and (ii) a wavelength conversion element that converts wavelengths of the light emitted by the light-emitting element, a globe that at least covers the light-emitting unit in light emission directions thereof, a second heat sink member that has a first part in surface contact with a region of the front surface of the mounting substrate where the light-emitting unit is not mounted and that has a second part in surface contact with the first heat sink member. 
     Advantageous Effects of Invention 
     According to research concerning heat sink structure, the inventors discovered that when a heat dispersal pathway originating at the light-emitting element mounting surface of a mounting substrate is secured, better heat dispersal characteristics can be obtained than by simply placing a large-volume heat sink at the surface opposite the light-emitting element mounting surface. The present invention, created according to this new knowledge, secures a heat dispersal pathway originating at the light-emitting element mounting surface of the mounting substrate by providing a second heat sink. According to this structure, a bulb-type lighting source with better heat dispersal characteristics than the conventional technology can be obtained. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  shows an exploded perspective view of the structure of the lamp pertaining to the embodiment of the present invention. 
         FIG. 2  shows a cross-section of the structure of the lamp pertaining to the embodiment of the present invention. 
         FIG. 3  shows a top view explaining the contact zone between the heat sink member and the mounting substrate. 
         FIG. 4  shows the heat dispersal pathways of the lamp pertaining to the embodiment of the present invention. 
         FIG. 5  schematically shows the experimental system for the heat dispersal characteristics. 
         FIGS. 6A through 6E  show graphs of the temperatures measured at each position as well as the junction temperatures. 
         FIGS. 7A through 7D  schematically show the experimental system for the heat dispersal characteristics. 
         FIG. 8  shows a graph of the temperatures measured for each version. 
         FIG. 9  shows a cross-section of the structure of the lamp pertaining to a variation of the present invention. 
         FIG. 10  shows a top view explaining the contact zone between the heat sink member and the mounting substrate. 
         FIG. 11  shows a cross-section of the structure of the lamp pertaining to a variation of the present invention. 
         FIGS. 12A and 12B  show cross-sections of the structure of lamps pertaining to variations of the present invention. 
         FIGS. 13A through 13C  show cross-sections of the structure of lamps pertaining to variations of the present invention. 
         FIG. 14  shows a cross-section of the structure of the lamp pertaining to a variation of the present invention. 
         FIG. 15  shows a cross-section of the structure of the lamp pertaining to a variation of the present invention. 
         FIG. 16  shows a cross-section of the structure of the lamp pertaining to a variation of the present invention. 
         FIG. 17  shows a cross-section of the structure of the lamp pertaining to a variation of the present invention. 
         FIG. 18  shows a cross-section of the structure of the lamp pertaining to a variation of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     A preferred embodiment of the present invention is described below with reference to the drawings. 
     (Structure) 
       FIG. 1  is an exploded perspective view showing the structure of the lamp pertaining to the present embodiment.  FIG. 2  is a cross-sectional diagram showing the structure of the lamp pertaining to the present embodiment. 
     As shown in  FIG. 1 , the lamp  1  includes a bowl-shaped case  15  to which the an Edison screw  16  is attached, a heat sink member  11  that closes the mouth of the case  15 , a mounting substrate  21  placed on the top surface (the surface opposite the surface that closes the mouth)  14  of the heat sink member  11 , a light-emitting unit  24  placed on the top surface (the surface opposite the surface that is in contact with the heat sink member  11 ) of the mounting substrate  21 , a heat sink member  31  that is placed on the top surface  14  of the heat sink member  11 , and a globe  41  that is fixed to the heat sink member  31  and covers the light-emitting unit  24  in the light emission direction thereof. Further, as shown in  FIG. 2 , the inside of the case  15  accommodates in an inner space thereof a power supply circuit  18  that supplies commercial power through the Edison screw  16  to the light-emitting unit  24 . The power supply circuit  18  is made up of several electronic components mounted on a printed circuit board  17 . The printed circuit board  17  is fixed to the interior of the case  15 . The power supply circuit  18  and the light-emitting unit  24  are electrically connected through a wire  19 . The wire  19  is passed through a through-hole  13  in the heat sink member  11  and through a through-hole  33  in the heat sink member  31 . The case  15  is made of plastic, ceramic, or similar electrically insulating material. It should be noted that the bowl shape here designates any shape such that the end opposite the end from which the Edison screw  16  protrudes forms a mouth and is not particularly limited to a shape with a round mouth. 
     The heat sink member  11  is made of a metal such as anodized aluminum in an approximately circular truncated cone shape where the side portions form fins  12  and where the top surface  14  is flat. In addition, a through-hole  13  is provided to allow a wire to be introduced. 
     The mounting substrate  21  is constructed from a metal substrate  22  that is made of aluminum, copper, or other metal and an insulating layer  23  that is made of plastic, ceramic or other insulator and which is layered on the top surface (the surface opposite the surface that is in contact with the heat sink member  11 ) of the metal substrate  22 . The light-emitting unit  24  and electrode pads  27  are mounted on the insulating layer  23 . The perimeter  28  of the top surface of the mounting substrate  21  is the region in which the light-emitting unit  24  is not placed. The perimeter  28  has no insulating layer  23  and so the top surface of the metal substrate  22  is exposed. 
     The light-emitting unit  24  is composed of an LED  25  and a silicone resin body  26  (see  FIG. 2 , enlargement A). The LED  25  is a light-emitting element that emits blue light. The silicone resin body  26  contains yellow phosphors and functions as a wavelength conversion element by converting blue light into yellow light. 
     The heat sink member  31  is made of a metal such as anodized aluminum and is shaped like a roughly circular flat disc where the bottom surface has a recess  34 . A portion of the recess  34  continues through to the top surface of the disc, thus forming an aperture  32 . The bottom surface of the heat sink member  31  is in surface contact with the top surface  14  of the heat sink member  11 . The recess  34  of the heat sink member  31  is shaped so that the mounting substrate  21  can be accommodated therein while the perimeter  28  of the top surface of the mounting substrate  21  remains in surface contact. Also, the aperture  32  of the heat sink member  31  is shaped so as to accommodate the light-emitting unit  24 . 
     The globe  41  is made of a translucent material such as plastic or glass, and is attached to the heat sink member  31  in such a manner that the light-emitting unit  24  and the mounting substrate  21  are covered from the top in order to protect the light-emitting unit  24  and the mounting substrate  21  from direct contact by a user and from scattered water or the like. It should be noted that attaching the globe  41  to the top surface of the heat sink member  31  is accomplished by joining the two with a thermally conducting joining material, or else by inserting a screw into a screw groove in the heat sink member  31 . The perimeter  35  of the heat sink member  31  is the portion that is not covered by the globe  41  and that is in contact with outside air (see  FIG. 2 ). 
     The relationship between the heat sink member  31  and the mounting substrate  21  is explained below. 
       FIG. 3  is a diagram showing a top view of the contact zone between the heat sink member  31  and the mounting substrate  21 . 
     According to the present embodiment, the contact area between the mounting substrate  21  and the heat sink member  31  is greater than the area on which the heat source, namely the light-emitting unit  24 , is placed. The rise in temperature of the light-emitting unit  24  can be substantially inhibited by widening the contact area between the mounting substrate  21  and the heat sink member  31  in this way. 
     In addition, the mounting substrate  21  is a quadrilateral when seen from above. The heat sink member  31  is in surface contact with three sides of the perimeter  28  of the mounting substrate  21 . Using a metal-based mounting substrate as the mounting substrate on which to place the light-emitting unit, better heat dispersal characteristics can be obtained in comparison to using a ceramic base. However, a metal-based mounting substrate has a drawback in that, when there is a temperature difference between the top surface and the bottom surface, internal stresses caused by differential thermal expansion lead to warpage. Should warpage of the mounting substrate occur, the contact area between the bottom surface of the mounting substrate and the heat sink member will be reduced, and the heat dispersal characteristics deteriorate. According to the present embodiment, the heat sink member  31  is in surface contact with the top surface of the mounting substrate  21  and thus, temperature differences between the top surface and the bottom surface of the mounting substrate  21  are inhibited, and even if internal stresses are caused by a difference in temperature, warpage can be controlled by the downward press on the top surface of the mounting substrate  21 . Furthermore, according to the present embodiment, the heat sink member  31  is in surface contact with three sides of the perimeter  28  of the mounting substrate  21  and thus can enhance the effective control of any warpage in the mounting substrate  21 . 
     In addition, according to the present embodiment, the thickness T 2  of the portion of the heat sink member  31  that is in surface contact with the top surface of the mounting substrate  21  is greater than the thickness T 1  of the mounting substrate  21  (see  FIG. 2 , enlargement A). Increasing the thickness T 2  of the heat sink member  31  in this way can enhance the stiffness of the heat sink member  31  which in turn can further enhance the effective control of any warpage in the mounting substrate  21 . 
     In addition, according to the present embodiment, the heat sink member  31  is in direct contact with the metal substrate  22  without involving the insulating layer  23  (see  FIG. 2 , enlargement A). Accordingly, thermal resistance at the interface between the mounting substrate  21  and the heat sink member  31  can be reduced, and thus better heat dispersal characteristics can be achieved. 
       FIG. 4  is a diagram showing the heat dispersal pathways of the lamp pertaining to the present embodiment. 
     The mounting substrate  21  has the following heat dispersal pathways: a pathway which originates at the bottom surface and in which heat is conducted to the heat sink member  11  (reference sign  51 ) and the heat sink member  11  is naturally cooled (reference sign  52 ); a pathway which originates at the top surface and in which heat is conducted to the heat sink member  31  (reference sign  53 ) and the heat sink member  31  is naturally cooled (reference sign  54 ); and a pathway which originates at the top surface and in which heat is conducted to the heat sink member  31  (reference sign  53 ), then heat is conducted by the heat sink member  31  to the heat sink member  11  (reference sign  55 ) and the heat sink member  11  is naturally cooled (reference sign  52 ). Thus, according to the present embodiment, not only the bottom surface but also the top surface of the mounting substrate  21  are both at the origin of heat dispersal pathways. 
     The heat dispersal characteristics of the heat dispersal pathway originating at the top surface of the mounting substrate  21  are validated below according to experimental results. 
     (Validation) 
     The inventors first conducted an experiment concerning changes in the heat dispersal characteristics exhibited along with changes in the enveloping volume of a heat sink member placed at the bottom surface of a mounting substrate. 
       FIG. 5  is a diagram schematically illustrating the experimental system for the heat dispersal characteristics. 
     The sample LED module is prepared by placing a light-emitting unit  64  on a mounting substrate  62 . The heat sink member  61  is placed at the bottom surface of the mounting substrate  62 . An aluminum substrate is used for the mounting substrate  62  and an LED chip 1.0 mm square is used as the light-emitting element of the light-emitting unit  64 . Twelve LED chips are flip-chip mounted on the aluminum substrate. 
     In this experimental system, four types of heat sink member, differing by enveloping volume, were prepared (enveloping volumes: 54 cm 3 , 208 cm 3 , 1108.8 cm 3 , 2625 cm 3 ). When current was applied to the light-emitting unit  64 , the temperature was measured at each of four positions (Pos.  1  at the top surface of the sample, Pos.  2  at the top surface of the heat sink member next to the sample, Pos.  3  at the edge of the top surface of the heat sink member, Pos.  4  at the bottom surface of the heat sink member) and the LED chip junction temperature T j  was also measured. The current applied to the light-emitting unit  64  was one of three types, measuring 100 mA, 150 mA, and 200 mA, respectively. 
       FIGS. 6A through 6E  show graphs indicating the temperatures measured at each position as well as the junction temperatures, where  FIG. 6A  shows the temperatures at Pos.  1  at the top surface of the sample,  FIG. 6B  shows the temperatures at Pos.  2  at the top surface of the heat sink member next to the sample,  FIG. 6C  shows the temperatures at Pos.  3  at the edge of the top surface of the heat sink member,  FIG. 6D  shows the temperatures at Pos.  4  at the bottom surface of the heat sink member, and  FIG. 6E  shows the LED chip junction temperatures. 
     From these results, it is understood that the temperature at each position decreases as the enveloping volume of the heat sink member that is placed at the bottom surface of the mounting substrate increases. However, the effect of the drop in temperature obtained by increasing the enveloping volume diminishes along with the increasing enveloping volume. For example, a tremendous drop in temperature can be obtained at Pos.  1  at the top surface of the sample by changing the enveloping volume of the heat sink member from 54 cm 3  to 208 cm 3 . Yet, hardly any drop in temperature can be obtained by changing the enveloping volume of the heat sink member from 1108.8 cm 3  to 2625 cm 3 . This trend can be observed at Pos.  2  next to the sample, at Pos.  3  at the edge of the top surface of the heat sink member, and at Pos.  4  at the bottom surface of the heat sink member, but is particularly striking at Pos.  1  at the top surface of the sample. Also, the same trend seen at Pos.  1  at the top surface of the sample can be seen in the junction temperature T j . 
     From the above, it is understood that while it is possible to obtain a decrease in temperature by increasing the enveloping volume of the heat sink member that is placed at the bottom surface of the mounting substrate, there is a limit to this effect. Given that the heat dispersal effect is constrained by the enveloping volume of the heat sink member when that volume is small, it can be surmised that when the enveloping volume reaches a certain value, the heat dispersal effect is constrained by the contact area between the mounting substrate and the heat sink member. Upon reaching these results, the inventors conducted an experiment concerning changes in the heat dispersal characteristics exhibited along with changes in the contact area between the mounting substrate and the heat sink member while the enveloping volume of the heat sink member is held constant. 
       FIGS. 7A through 7D  are diagrams schematically illustrating the experimental system for the heat dispersal characteristics, where  FIG. 7A  shows the sample dimensions of the LED module,  FIG. 7B  shows version  1  of the system,  FIG. 7C  shows version  2  of the system, and  FIG. 7D  shows version  3  of the system. 
     In version  1 , the heat sink member is placed only at the bottom surface of the mounting substrate, and the enveloping volume of the heat sink member is 200 cm 3 . In version  2 , the heat sink member is placed only at the bottom surface of the mounting substrate, and the enveloping volume of the heat sink member is 300 cm 3 . In version  3 , the heat sink member is placed at the bottom surface and at the top surface of the mounting substrate, and the enveloping volume of the heat sink member is 300 cm 3 . 
       FIG. 8  is a graph showing the temperatures that were measured for each version. 
     Comparing version  1  to versions  2  and  3 , it is understood that changing the enveloping volume of the heat sink member from 200 cm 3  to 300 cm 3  caused a drop in sample top surface temperature. Further comparing version  2  and version  3 , it is understood that even when the enveloping volume of the heat sink member is held constant at 300 cm 3 , a greater drop in sample top surface temperature occurs in version  3 , where the heat sink member is placed at the bottom surface and at the top surface of the mounting substrate, in contrast to version  2 , where the heat sink member is placed only at the bottom surface of the mounting substrate. That is, it is understood that when a heat dispersal pathway (thermal transmission pathway) originating at the top surface of the mounting substrate is secured, better heat dispersal characteristics can be obtained than by simply increasing the enveloping volume of a heat sink member placed at the bottom surface of the mounting substrate. 
     Version  1  and version  2  above correspond to conventional technology, and version  3  corresponds to the present embodiment. Thus, according to the present embodiment, better heat dispersal characteristics than those of conventional technologies can be obtained, and this can in turn contribute to the miniaturization of the lamp. 
     The lamp pertaining to the present invention was described above according to a single embodiment, but the present invention is not limited to this embodiment. For example, the following variations are plausible: 
     1) In the present embodiment, the electrode pads  27  are placed on the top surface of the mounting substrate  21 , and the wire  19  is connected to the electrode pads  27  on the top surface of the mounting substrate  21 . However, the present invention is not limited in this way. For example, as shown in  FIG. 9 , the electrode pads  27  may be placed on the bottom surface of the mounting substrate  21 , the wiring pattern  29  and the electrode pads  27  may be electrically connected through a through-hole, and the wire  19  may be connected to the electrode pads  27  on the bottom surface of the mounting substrate  21 . This arrangement makes possible the enlargement of the region of the top surface of the mounting substrate  21  in which the light-emitting unit is not placed, as shown in  FIG. 10 . This in turn allows the heat sink member  31  to be placed in quadrilateral surface contact with the mounting substrate  21 . Also, as shown in  FIG. 11 , there may be a through-hole going through the mounting substrate  21  from the top surface to the bottom surface, and the wire  19  may be passed through this through-hole. 
     2) In the present embodiment, the heat sink member  31  has no fins. However, the present invention is not limited in this way. For example, as shown in  FIG. 12A , the side portions of the heat sink member  31  may have fins  36 . Also, in the present embodiment, the side portions of the heat sink member  11  have fins. However, the present invention is not limited in this way. For example, as shown in  FIG. 12B , the inside of the heat sink member  11  may have fins  12 . 
     3) In the present embodiment, the globe  41  is in a shaped to resemble a light bulb. However, the present invention is not limited in this way. For example, as shown in  FIGS. 13A through 13C , the globe  41  may be made as small as possible in order to increase the portion of the heat sink member  31  that is in contact with ambient air. 
     4) In the present embodiment, the inner circumference of the aperture of the heat sink member  31  is uniform at all points. However, the present invention is not limited in this way. For example, as shown in  FIG. 14 , the aperture may have an inner surface  37  that widens as it approaches the top surface of the heat sink member. In this manner, light output efficacy may be increased. 
     5) In the present embodiment, a metal-based mounting substrate is used. However, the present invention is not limited in this way. For example, a ceramic substrate equivalent to the aluminum substrate may be used to produce the same effect. 
     6) In the present embodiment, the top surface of the heat sink member  11  is flat and the bottom surface of the heat sink member  31  has a recess to accommodate therein the mounting substrate  21 . However, the present invention is not limited in this way. For example, the top surface of heat sink member  11  may have a recess to accommodate therein the mounting substrate  21 , and the heat sink member  31  may only have an aperture to accommodate the light-emitting unit  24  and allow light output. Also, the top surface of the heat sink member  11  and the bottom surface of the heat sink member  31  may both have a recess so that the mounting substrate  21  can be accommodated in both recesses. 
     7) In the present embodiment, the light-emitting unit  24  is accommodated completely within the aperture of the heat sink member  31 . However, the present invention is not limited in this way. For example, as shown in  FIG. 15 , the surface  39  of the top part of the light-emitting unit  24  may protrude beyond the surface  38  of the heat sink member  31  in a perpendicular direction from the insulating base  21 . In this manner, the light output efficacy may be increased. It should be noted that in this configuration, the stiffness of the heat sink member  31  can be enhanced by making the thickness T 2  of the heat sink member  31  greater than the thickness T 1  of the mounting substrate  21  which can in turn preserve the effective control of any warpage in the mounting substrate  21 . 
     8) In the present embodiment, nothing is stated about the gas in the inner space of the globe  41 . This gas may be air, or else a nitrogen gas may be sealed inside. As nitrogen gas is a better thermal conductor than air, even better heat dispersal characteristics can be achieved with a nitrogen gas sealed inside. Also, luminous deterioration due to moisture absorption by the LEDs and the phosphors can be prevented. 
     Note that the LED and phosphors may be prevented from absorbing moisture by evacuating all gas and creating a vacuum in the inner space of the globe  21 . 
     The sealing of the inner space of the globe  41  may be realized as shown in  FIGS. 16 ,  17 , and  18 . In  FIG. 16 , the seal is realized via a sealer  43  that is applied to the opening of the through-hole  13  in the heat sink  11  plus a seal valve  42  on the globe  41 . In  FIG. 17 , a seal valve  42  is placed at the opening of the through-hole  13 . Also, in  FIG. 18 , a seal valve  42  is placed at the opening of the through-hole  33 . A mechanical vacuum valve or similar part may, for example, be used as the seal valve  42 . Glass, plastic, cement, or similar materials may be used as the sealer  43 . 
     9) In the present embodiment, the LED  25  is sealed by a silicone resin body  26 . However, the present invention is not limited in this way. For example, as shown in  FIG. 18 , the LED  25  may be exposed. In this configuration, the inner surface of the globe  41  has a phosphor layer  44  which allows white light to be produced, much like in the present embodiment. Also, in order to prevent moisture absorption by the LED and phosphors, it is desirable to seal nitrogen gas or dry air into the inner space of the globe  41 , or else to evacuate all gas from inside and create a vacuum. 
     [Industrial Applicability] 
     The present invention can be used widely and generally in lighting applications. 
     [Reference Signs List] 
       1  lamp 
       11  heat sink member 
       12  fins 
       13  through-hole 
       14  top surface 
       15  case 
       16  Edison screw 
       17  printed circuit board 
       18  power supply circuit 
       19  wire 
       21  mounting substrate 
       22  metal substrate 
       23  insulating layer 
       24  light-emitting unit 
       25  LED 
       26  silicone resin body 
       27  electrode pads 
       28  perimeter 
       29  wiring pattern 
       31  heat sink member 
       32  aperture 
       33  through-hole 
       34  recess 
       35  perimeter 
       36  fins 
       37  gradually-widening inner surface 
       38  surface of the heat sink member 
       39  top surface of the light-emitting unit 
       41  globe 
       42  seal valve 
       43  sealer 
       44  phosphors 
       61  heat sink member 
       62  mounting substrate 
       64  light-emitting unit