Abstract:
Disclosed is a light source device that is a globe-type light source that uses a laser diode (LD) and that obtains white light emission with a high light flux and is almost uniform in all directions. The light source device has a dual-tube structure comprising a transparent light-emitting tube ( 11 ) and a transparent outer tube ( 15 ). The light-emitting tube ( 11 ) is sealed ( 112 ) and the tip of the straight tube ( 111 ) is rounded. A fluorescent material layer ( 12 ) is formed on an inner surface of a light-emitting region ( 11   a ) in the light-emitting tube ( 11 ) in the vicinity of the seal ( 112 ) and a reflective film ( 13 ) is formed on an inner surface of a straight tube region ( 11   b ) which is a non-light-emitting section of the light-emitting tube ( 11 ). The outer tube ( 15 ) is frosted ( 151 ). The LD ( 16 ) with suppressed temperature increase and attached to a heat radiator ( 17 ) is disposed on the release end section of the light-emitting tube ( 11 ) and the fluorescent material emits light by the LD ( 16 ) radiating laser light on the fluorescent material layer ( 12 ). This enables white light emission that has high light flux and is almost uniform in all direction to be obtained while using an LD.

Description:
TECHNICAL FIELD 
       [0001]    Embodiments according to the present invention relate to a globe-type light source device that emits a light generated from a laser diode (LD) as an excitation light of a fluorescent material on the fluorescent material, thereby to obtain a white light. 
       BACKGROUND ART 
       [0002]    Conventionally, a light source device using ultraviolet light emitting diode (UV-LED) and blue light emitting diode radiates a ultraviolet light and a blue light on a fluorescent material, thereby to emit a white light. 
       CITATION LIST 
     Patent Literature 
       [0000]    
       
         PLT 1: Japanese Patent Application Laid-Open No. 2001-156338 
       
     
       SUMMARY OF THE INVENTION 
     Technical Problem 
       [0004]    The technique in Patent Literature 1 has an advantage that since a ultraviolet light is radiated toward a fluorescent material layer on the inner surface of the tip of a glass tube from a UV-LED and a visible light is radiated from a fluorescent material, any emitting color can be obtained by adjusting a blend rate of the fluorescent material at lower consumed power than a filament lamp and mercury is not used thereby to be more environmentally friendly than a mercury fluorescent lamp. 
         [0005]    However, a ultraviolet light radiated from the UV-LED is applied only on the top of the glass tube, and thus only the top of the glass tube emits a light and is poor-looking, and a LED chip is floating inside the glass tube so that a temperature of the LED chip easily increases, and there is therefore a problem that a large amount of power is difficult to power into the UV-LED and a light with a high light flux cannot be obtained. 
         [0006]    The embodiments are directed for providing a light source device capable of obtaining white light emission which is with a high light flux and is almost uniform in all directions. 
       Solution to Problem 
       [0007]    According to the embodiments, there are provided a light emitting tube which is formed by sealing one end as the tip of a translucent straight tube, a fluorescent material layer formed on the tip of the light emitting tube, a laser diode which is arranged inside an open end at the other end of the straight tube and radiates a laser light on the fluorescent material layer, and a heat radiator which supports the laser diode and restricts heat generation of the diode. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is an outer profile view for explaining alight source device according to a first embodiment. 
           [0009]      FIG. 2  is a cross-section view for explaining a structure of  FIG. 1 . 
           [0010]      FIG. 3  is a cross-section view illustrating enlarged essential parts of  FIG. 2 . 
           [0011]      FIG. 4  is a cross-section view for explaining a light source device according to a second embodiment. 
           [0012]      FIG. 5  is a cross-section view for explaining a light source device according to a third embodiment. 
           [0013]      FIG. 6  is an outer profile view for explaining a light source device according to a fourth embodiment. 
           [0014]      FIG. 7  is a top view of  FIG. 6 . 
           [0015]      FIG. 8  is a cross-section view taken along the line Ia-Ib of  FIG. 7 . 
           [0016]      FIG. 9  is a top view with a light emitting tube and a protective cover removed. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0017]    Embodiments will be described below in detail with reference to the drawings. 
       First Embodiment 
       [0018]      FIG. 1  and  FIG. 2  explain a light source device according to a first embodiment, where  FIG. 1  is an outer profile view and  FIG. 2  is a cross-section view for explaining an inner surface structure of  FIG. 1 . 
         [0019]    In  FIG. 1  and  FIG. 2 ,  11  denotes a light emitting tube one end of a straight tube  111  of which is sealed  112  to be rounded and which is made of quartz glass, borosilicate glass or transparent resin, for example. A fluorescent material layer  12  applied with a fluorescent material is formed on the inner surface of a light emitting region  11   a  at the tip of the light emitting tube  11 . A reflective film  13  such as barium sulfate layer is formed between the light emitting region  11   a  of the light emitting tube  11  and the inner surface of a straight tube region  11   b  at the other end side. 
         [0020]      14  denotes a support member made of, for example, synthetic resin which is heat resistant and on which an opening  141  is formed at the center. An open end of the light emitting tube  11  in the straight tube region  11   b  is attached to a stepped support portion  142  formed on the opening  141  by use of a fixing means such as adhesive. The stepped support portion  142  is formed on the opening  141 , but may have a groove shape according to the shape of an open portion of the light emitting tube  11 . 
         [0021]      15  denotes a filament lamp-shaped outer tube made of glass or translucent resin having a translucency, for example, in which the light emitting tube  11  is housed. The outer tube  15  is formed of a dome-shaped light emitting region  15   a  as a light emitting portion and a base region  15   b  as an attachment portion, and an open end of the outer tube  15  in the base region  15   b  is attached to a support portion  143  formed on the support member  14  by use of a fixing means such as adhesive. The support portion  143  is formed in a groove shape according to the open portion of the outer tube  15 , but may be formed with a step outside the support member  14  like the support portion  142  supporting the light emitting tube  11 . The inner surface of the outer tube  15  is frosted  151  for diffusing an incident light. 
         [0022]    The outer tube  15  is designed to be similar to a current filament lamp in its outer profile, and is not necessarily needed. The outer surface of the outer tube  15  is frosted  151  to have a similar diffusion effect. 
         [0023]      16  denotes a LD arranged inside the open end of the light emitting tube  11  in a state in which a radiation portion for emitting a laser light is opposed to the fluorescent material layer  12 . The LD  16  is attached on an attachment portion  171  formed on part of a heat radiator  17  which partially passes inside the opening  141  of the support member  14  and which incorporates a power supply circuit (not illustrated) for acquiring a DC voltage necessary for driving the LD  16 . 
         [0024]    The LD  16  has a fan-shaped light distribution of about 10°, for example. The light distribution angles of the LD are different between about 10° in the horizontal direction and about 40° in the vertical direction and a radiation area is rectangular, but an explanation will be made assuming an angle of 10°. 
         [0025]      18  denotes a bottomed conductive nozzle through which the heat radiator  17  is housed. A male screw  181  is formed on the outer periphery of the nozzle and a throughhole  182  is formed on the bottom thereof. The nozzle  18  is electrically connected to one input end of the power supply circuit. An open end of the nozzle  18  is attached to the groove formed on the support member  14  by use of a fixing means such as adhesive. 
         [0026]    The throughhole  182  is fixed with an electrode  20  which is electrically connected to the other input end of the power supply circuit via an insulative material  19  for insulation from the nozzle  18 . Thereby, the nozzle  18  and the electrode  20  are electrically connected to the power supply circuit so that the support member  14 , the light emitting tube  11  and the outer tube  15  are integrally configured. 
         [0027]      22  denotes an insulative socket which is bottomed and cylindrical. A conductive receiving port  23  formed with a female screw  231  into which the male screw  181  of the nozzle  18  is screwed is attached on the inner surface of the socket  22 . The socket is arranged at the bottom with a connection terminal  24  electrically connected to an electrode  19  with the nozzle  18  screwed. Typically, the socket  22  is attached on the lamp fitting side and the nozzle is detachably attached to the fitting. 
         [0028]    The nozzle  18  is connected to one electrode of an AC power supply  25  and the connection terminal  24  is connected to the other electrode of the AC power supply  25 . The AC power supply  25  is supplied to the power supply circuit to be converted from AC to DC, and can supply drive power to the LD  16 . 
         [0029]    Light emission of the light source device of  FIG. 2  will be described with reference to  FIG. 3  illustrating the enlarged light emitting tube  11  of  FIG. 2 . 
         [0030]    At first, when an AC voltage of the AC power supply  25  is supplied to the power supply circuit housed in the heat radiator  17 , it is converted into a DC voltage in the power supply circuit. The DC voltage is supplied to the LD  16  so that the LD  16  radiates a VU laser light. The laser light travels inside the light emitting tube  11  with a directivity of about 10°, and finally reaches the fluorescent material layer  12  at the tip to be absorbed in the fluorescent material layer  12 , thereby emitting a white light. The white light is radiated on the outer tube  15  side based on the light emission of the fluorescent material layer  12 . 
         [0031]    A laser light which is reflected instead of being absorbed in the fluorescent material layer  12  indicated with broken arrows in  FIG. 3  and a laser light spreading at more than 10° from the LD  16  indicated in chained lines are reflected on the reflective film  13  to be radiated on the fluorescent material layer  12  again, thereby being converted into a white light. 
         [0032]    In this way, the laser light radiated from the LD  16  is radiated at a fan-shaped light distribution of about 10°, and the reflective film  13  is formed on the inner surface of the straight tube region  11   b  of the light emitting tube  11  so that a band-like strong light is emitted only in the light emitting region  11   a  at the tip of the light emitting tube  11 . When this is viewed over the outer tube  15 , it seems as if a filament was lighting in a filament lamp. 
         [0033]    The white light radiated on the outer tube  15  side is diffused by the frosting  151  formed on the inner surface of the outer tube  15  thereby to obtain a similar illuminance from the outside of the outer tube  15 . 
         [0034]    According to the embodiment, a LD having a stronger directivity than a LED is used as a fluorescent material excitation light source, thereby efficiently guiding a laser light up to a fluorescent material applied portion at the tip of the light emitting tube. Since the LD can be arranged at the end of the light source, heat radiation from the LD can be easily performed by a heat radiating means such as heat radiator, thereby applying more power and obtaining a light with a higher light flux. 
         [0035]    A conceptual example of a method for forming the light emitting tube  11  according to the embodiment illustrated in  FIG. 2  will be described with reference to the following respective steps (1) to (5). 
         [0036]    (1) Heat one end of the glass tube of the straight tube with a burner. 
         [0037]    (2) Put the other end of the glass tube in a preheated metal mold, put high-pressure air into the glass tube, and round the light emitting region  11   a.    
         [0038]    (3) Slowly cool the tip of the glass tube such that no distortion remains. 
         [0039]    (4) Form the fluorescent material layer  12  on the inner surface as the light emitting region  11   a.    
         [0040]    (5) Form a barium sulfate layer as the reflective film  13  on the inner surface of the straight tube region  11   b  as the straight tube inside the glass tube. 
         [0041]    In this way, the fluorescent material layer  12  and the reflective film  13  can be formed inside the light emitting tube  11  through the respective steps (1) to (5). 
         [0042]    A two-layer structure including the fluorescent material layer  12  may be employed in the step (5) of forming the reflective film  13  as the barium sulfate layer. In this case, the fluorescent material layer  12  is formed to be positioned on the glass tube side. 
         [0043]    A conceptual example of a method for forming the fluorescent material layer  12  and the reflective film  13  in the light emitting tube  11  in the straight tube region  11   b  will be described below with reference to the following respective steps (a) to (f). 
         [0044]    (a) Flow, into the glass tube, fluorescent slurry made of fluorescent powder having, for example, a mix ratio (I:II) at which an apatite-based blue fluorescent material (I) and a silicate-based yellow fluorescent material (II) have optimum color temperatures such as (90 wt/%:10 wt/%) to (95 wt/%:5 wt/%), and a solvent of, for example, butyl acetate, soluble nitrocellulose and calcium pyrophosphate. 
         [0045]    (b) Face the tip of the light emitting tube  11  upward, feed drying air into the light emitting tube  11  by use of a thin metal pipe, and dry the fluorescent material. 
         [0046]    (c) Scrape the fluorescent material positioned in the straight tube region  11   b  by use of a thin comb-shaped jig. 
         [0047]    (d) Face the tip of the light emitting tube  11  upward, immerse the straight tube region  11   b  into barium sulfate slurry made of barium sulfate powder and solvent (butyl acetate, soluble nitrocellulose and calcium pyrophosphate). When immersed, if a pressure inside the light emitting tube  11  is the same as an atmosphere pressure, the barium sulfate slurry cannot enter the light emitting tube  11 . The light emitting tube  11  is immersed into the barium sulfate slurry with a metal rod put inside the light emitting tube  11 , the metal rod is picked out with the light emitting tube  11  immersed and the pressure inside the light emitting tube  11  is lowered, thereby flowing the barium sulfate slurry into the light emitting tube  11 . 
         [0048]    (e) Face the tip of the light emitting tube  11  upward, feed drying air into the light emitting tube by use of a thin metal pipe, and dry the barium sulfate layer. 
         [0049]    (f) Heat the light emitting tube  11  at about 500° C. for 10 minutes, remove the solvent inside the fluorescent material layer  12  and the barium sulfate layer, and dissolve a binder to fix a fluorescent material and barium sulfate onto the inner surface of the light emitting tube. 
         [0050]    There is an advantage that when the barium sulfate layer formed in the straight tube region  11   b  is formed on the fluorescent material layer  12 , the step (c) can be omitted. 
         [0051]    The fluorescent material layer and the reflective film layer are provided inside the straight tube in the above description, but may be provided outside the straight tube. Also in this case, a similar effect can be obtained as when they are provided inside the straight tube. 
         [0052]    A combination of a laser light wavelength and a fluorescent material may be a combination of a laser light with a wavelength of 405 nm, an apatite-based blue fluorescent material and a silicate-based yellow fluorescent material, a combination of a laser light with a wavelength of 455 nm and a silicate-based yellow fluorescent material, a combination of a laser light with a wavelength of 455 nm and a YGA-based yellow fluorescent material, and the like. 
       Second Embodiment 
       [0053]      FIG. 4  explains a light source device according to a second embodiment. The embodiment obtains safety when a light source using LD is configured. Like reference numerals are denoted to like reference parts identical to those in the above embodiment, and an explanation thereof will be omitted. This is also applicable to the following embodiments. 
         [0054]    The light source device is provided with a sensor  41  for detecting an abnormality mode when the light emitting tube  11  or the outer tube  15  comes off the support member  14  during drive or when an unusual impact or outer pressure, which can cause either the light emitting tube  11  or the outer tube  15  to break, is applied or either one breaks. The sensor  41  may be a sound sensor for detecting a glass breaking sound and outputting a detection signal, or a vibration impact sensor for detecting a vibration occurring due to application of an impact or outer pressure and outputting a detection signal. 
         [0055]    When the sensor  41  detects the abnormality mode, a detection signal is output from the sensor  41 . The power supply circuit is stopped based on the detected signal thereby to stop the LD  16 . The radiation of a laser light from the LD  16  is stopped thereby to eliminate safety problems when the light emitting tube  11  or the outer tube  15  breaks. 
       Third Embodiment 
       [0056]      FIG. 5  explains a light source device according to the third embodiment. The embodiment is such that the light emitting region  11   a  of the light emitting tube  11  is formed in a dome shape so that its outer side is larger than the outer shape of the straight tube region  11   b . In this case, the light emitting region  11   a  is larger than the outer shape of the straight tube region  11   b  and correspondingly the fluorescent material layer  12  also spreads outside. 
         [0057]    In the embodiment, a white light can be emitted also toward the nozzle  18  as indicated in white arrows in the figure, thereby realizing a lamp closer to a filament lamp. Thus, a reflector can be efficiently used in a downlight with the reflector. 
       Fourth Embodiment 
       [0058]      FIGS. 6 to 9  explain a light source device according to a fourth embodiment, where  FIG. 6  is an outer profile view,  FIG. 7  is a top view of  FIG. 6 ,  FIG. 8  is a cross-section view taken along the line Ia-Ib of  FIG. 7 , and  FIG. 9  is a top view with the light emitting tube and the protective cover of  FIG. 7  removed. The embodiment employs a plurality of LDs. 
         [0059]    An outer profile of the embodiment will be described first with reference to  FIG. 6  and  FIG. 7 .  61  denotes a heat radiating plate also as a pedestal. A protective cover  62  is attached on the heat radiating plate  61 . For example, a quartz glass light emitting tube  63  in a dome shape is further held by four holding members  64  arranged at substantially uniform intervals on the protective cover  62 . At least two of the four holding members are removable or movable in their hook portions, and thus the light emitting tube  63  can be attached and detached. A fluorescent material layer  65  is applied on the inner surface of the light emitting tube  63 . 
         [0060]    The four holding members are employed, but more or less holding members may be employed, or the number is not limited and any number of holding members capable of holding the light emitting tube  63  is possible. 
         [0061]    As illustrated in  FIG. 8  and  FIG. 9 , a reflector  81  in an eight-sided pyramid shape is arranged at the center on the heat radiating plate  61  in the protective cover  62 . The surface of the reflector  81  is subjected to silver deposition known as a material capable of efficiently reflecting a laser light. The protective cover  62  opposite to the reflector  81  is formed with an illumination hole  621  for passing a laser light. 
         [0062]    The corresponding LDs  16  are attached onto the heat radiating plate  61  radially arranged at predetermined intervals from the reflective surface of the reflector  81 . Light guide members  82  which have a rod shape and are made of quartz glass, for example, are arranged between the laser light output units of the LDs  16  and the reflector  81 . The light guide member  82  is attached to a support portion  83  attached on the heat radiating plate  61 . 
         [0063]    In the thus-configured light source device, laser lights are radiated all together from the LDs  16  supplied with a DC voltage from the power supply circuit. The laser light is reflected on the corresponding reflector  81  via the light guide member  82 , and emits on a fluorescent material  65  on the inner surface of the light emitting tube  63  via the illumination hole  621  to be radiated to the outside from the light emitting tube  63 . 
         [0064]    According to the embodiment, laser rights are radiated from eight LDs via the light guide members so that the respective LDs can be arranged away from each other, thereby restricting a temperature of the LDs to be low. Consequently, an efficient light source with a high light flux and a large amount of light can be realized. Thereby, a mercury-free light source with low power consumption can be obtained. 
         [0065]    When the angles of the eight reflective surfaces of the reflector  81  are changed, the effect of the frosting  151  applied on the inner surface of the outer tube  15  in  FIG. 2  can be maintained. Fins or the like are formed on the heat radiating plate  61  to increase the surface area, thereby enhancing a heat radiating effect so that power capable of being applied to the LDs  16  can be increased, thereby enhancing an illuminance. 
         [0066]    A plurality of LDs, not limited to eight, may be arranged at different positions in the embodiment. The LDs are arranged in a balanced manner so that an influence of heat generation between the LDs can be restricted, thereby contributing to an increase in light emission efficiency. Since the laser light emitted from the LD is excellent in linearity, the light guide member  82  is not necessarily needed, and may be omitted and the laser lights may be directly reflected on the reflector. 
         [0067]    Some embodiments have been described above, but the embodiments are exemplary and do not intend to limit the scope of the invention. The novel embodiments may be performed in other various forms, and can be variously omitted, replaced or changed without departing from the spirit of the invention. The embodiments or their variants are encompassed in the scope or spirit of the invention, and are encompassed in the invention described in Claims and their equivalents. 
       REFERENCE SIGN LIST 
       [0000]    
       
           11 ,  63 : Light emitting tube 
           111 : Straight tube 
           112 : Seal 
           11   a : Light emitting region 
           11   b : Straight tube region 
           12 : Fluorescent material layer 
           13 : Reflective film 
           14 : Support member 
           15 : Outer tube 
           151 : Frost 
           15   a : Light emitting region 
           16 : LD 
           17 : Heat radiator 
           171 : Attachment portion 
           18 : Nozzle 
           181 : Male screw 
           20 : Electrode 
           22 : Socket 
           23 : Receiving port 
           231 : Female screw 
           61 : Heat radiating plate 
           65 : Fluorescent material layer 
           81 : Reflector 
           82 : Optical light guide member