Patent Publication Number: US-2009237597-A1

Title: Cold-cathode fluorescent lamp, backlight unit, and liquid crystal display

Description:
TECHNICAL FIELD 
     The present invention relates to a cold cathode fluorescent lamp (CCFL), a backlight unit that uses the CCFL as a light source, and a liquid crystal display (LCD) apparatus that includes the backlight unit. 
     BACKGROUND ART 
     A CCFL includes a tube-shaped glass bulb and a cold cathode type electrode sealed in the glass bulb at each end thereof. The electrode includes an electrode main body having a shape of, for example, a closed-bottom tube, and a lead wire attached to the bottom thereof, and one part of the lead wire is sealed to the end of the glass bulb, thus attaching the electrode to the glass bulb. 
     One example of an apparatus that uses this type of CCFL as a light source is a backlight unit of an LCD apparatus used in LCD televisions, etc. In recent years, there has been a decrease in the diameter of glass bulbs in CCFLs along with a reduction in the thickness of LCD apparatuses, and accordingly, the electrodes (main bodies) are becoming smaller, while the lead wires are becoming thinner. 
     Meanwhile, there is a tendency for LCD apparatuses not only to be thinner, but also to have increasingly large display panels, requiring a brighter light source and a larger amount of current to be applied to the CCFL. 
     For this reason, in CCFLs of recent years, the lead wires have an increasingly high electric current density due to the thinning of the lead wires and the increase in applied current, leading to a greater amount of heat generated in the lead wires while the lamp is lit. Note that the amount of heat generated in the electrode main body also increases due to the increase in applied current. This increase in the amount of heat generated by the electrode leads to a rise in the electrode temperature, ultimately leading to a shorter life and reduced efficiency of the lamp. 
     To suppress the rise in electrode temperature, there has been proposed a CCFL that includes a heat dissipater that has a larger diameter than the lead wire and that is on a portion of the lead wire that is outside the glass bulb, and the surface area has been increased to improve the heat dissipation characteristic (patent document 1). 
     Patent document 1: Japanese Patent Application Publication No. 2002-190279 
     DISCLOSURE OF THE INVENTION 
     Problems Solved by the Invention 
     However, the heat dissipation characteristic of the above CCFL is not sufficient, and the lead wire is easily broken. Specifically, although the heat dissipation characteristic improves when the outer diameter of the heat dissipater is larger than the lead wire and the dissipation surface area is larger in comparison to the lead wire, further enlargement of the heat dissipater (by outer diameter or length) is difficult, since it is necessary to store the CCFL in the backlight unit, ultimately leading to an insufficient heat dissipation characteristic. 
     Also, since the heat dissipater has been provided on the lead wire that extends out from an end of the CCFL and the lead wire has become thinner, if the heat dissipater touches a nearby member during assembly of the backlight unit, the lead wire breaks easily. 
     In view of the above, an object of the present invention is to provide a backlight unit and a CCFL that improves the heat dissipation characteristic without an increase in overall size, and furthermore, whose lead wire is not easily broken. 
     Means to Solve the Problems 
     In order to solve the above problems, the present invention is a cold cathode fluorescent lamp including a glass bulb; an electrode including an electrode main body and a lead wire, a portion of the lead wire having been sealed to an end of the glass bulb while the electrode main body is positioned in an interior of the glass bulb; and a heat dissipater provided on an other portion of the lead wire outside the glass bulb so as to, when viewed externally along an extending direction of the lead wire, surround the lead wire and be in contact with an outer surface of the end of the glass bulb. 
     Since the heat dissipater has direct contact with the ends of the glass bulb, this structure enables increasing the amount of heat that is directly transferred from the glass bulb to the heat dissipater. Also, since the lead wire is located in a polygon when the contact portion between the heat dissipater and the glass bulb is viewed externally along an extending direction of the lead wire, the lead wire is supported in a stable state. 
     Also, the heat dissipater may be tubular in shape, an end thereof being closed, and a surface of the closed end may be substantially in surface contact with the outer surface of the end of the glass bulb, or the heat dissipater may be columnar in shape, and the end thereof may be in surface contact with the outer surface of the glass bulb. 
     Furthermore, the heat dissipater may be composed of a conductive material, and the lead wire and the heat dissipater may be integrally formed as one piece. Also, the heat dissipater may conduct electricity and be electrically connected to the lead wire, and a conductive covering may be provided around the end of the glass bulb, the conductive covering being electrically connected to the heat dissipater. In addition, a face of the heat dissipater facing the glass bulb may conform in shape to the outer surface of the end of the glass bulb, and be in contact with the face of the glass bulb. In addition, the heat dissipater may be composed of solder. 
     Furthermore, the heat dissipater may include a first member composed of solder and a second member composed of a conductor other than solder, the second member being joined to the first member, and the first member may include the face of the heat dissipater that conforms to the shape of the end surface of the glass bulb, or the heat dissipater may include a conductor plate composed of a conductor other than solder, and a solder body that is joined to the solder, and the conductor plate may include the face of the heat dissipater that conforms to the shape of the end face of the glass bulb on a side that is opposite from the solder, and a plurality of through-holes may be formed in the conductor plate. 
     Also, the lead wire and the heat dissipater may be disposed with an interval therebetween, and be electrically connected to each other via solder, and the solder may be susceptible to melting down in a case of a flow of overcurrent due to joule heat, and furthermore the cold cathode fluorescent lamp may further include an insulation member that hermetically seals an area in the solder around connection portions between the lead wire and the heat dissipater. In addition, the insulation member may be a rosin. Also, the lead wire may include a bulge having a larger outer diameter than an outer diameter of the lead wire, and the bulge may be disposed so as to be in contact with the outer surface of the end of the glass bulb. 
     Meanwhile, in order to solve the above problem, the present invention is also a backlight unit including the cold cathode fluorescent lamp described above as a light source. 
     The present invention is also a backlight unit including a plurality of cold cathode fluorescent lamps as a light source; a housing that stores the plurality of cold cathode fluorescent lamps; a plurality of U-shaped lamp holders provided in the housing, each gripping an outer circumference of a different end of the plurality of cold cathode fluorescent lamps; and a lighting circuit for lighting the plurality of cold cathode fluorescent lamps, wherein each of the cold cathode fluorescent lamps is the cold cathode fluorescent lamp of claim  6 , each of the lamp holders is electrically connected to the respective one of the cold cathode fluorescent lamps by gripping an outer circumference of a covering thereof, the cold cathode fluorescent lamps have been gripped by the lamp holders so as to be arranged substantially parallel with an interval between two adjacent ones of the cold cathode fluorescent lamps, and a pair of lamp holders that grip the coverings of the two adjacent cold cathode fluorescent lamps on one side arranged substantially parallel are electrically connected to each other. 
     Alternatively, the present invention is also a backlight unit including a plurality of cold cathode fluorescent lamps as a light source; a housing that stores the plurality of cold cathode fluorescent lamps; a plurality of lamp holders provided in the housing, each holding a different end of the plurality of cold cathode fluorescent lamps; and a lighting circuit for lighting the plurality of cold cathode fluorescent lamps, wherein each of the cold cathode fluorescent lamps is the cold cathode fluorescent lamp of claim  6 , each of the lamp holders is electrically connected to the respective one of the cold cathode fluorescent lamps by being in contact with a covering thereof, the cold cathode fluorescent lamps are held by the lamp holders substantially parallel to two adjacent ones of the cold cathode fluorescent lamps with an interval therebetween, and a pair of lamp holders that hold the coverings of the two adjacent cold cathode fluorescent lamps arranged substantially parallel are electrically connected to each other on a grounded side, and a pair of the lamp holders that are in contact with the coverings at another end of the two adjacent ones of the cold cathode fluorescent lamps are connected on a high-voltage side to the lighting circuit. 
     Furthermore, the present invention is also a liquid crystal display apparatus that includes the backlight unit of claim  16 . Note that the “liquid crystal display apparatus” referred to here may be a liquid crystal color television, a liquid crystal monitor for a computer, or a compact display apparatus for portable or in-car use. 
     EFFECTS OF THE INVENTION 
     Since the CCFL pertaining to the present invention can increase an amount of heat transfer from a glass bulb to a heat dissipater, this CCFL enables improvement of a dissipation characteristic without enlarging a lamp diameter. Also, since a lead wire is supported by a contact portion between the heat dissipater and the glass bulb, deformation of the lead wire does not easily occur even when the heat dissipater touches another part etc., thereby reducing occurrences of lead wire breakage. 
     Even if the heat dissipater touches another part during assembly of the backlight unit, breakage of the electrode lead wire does not easily occur, and since the CCFL described above has been provided as a light source in the backlight unit pertaining to the present invention, improvement of the dissipation characteristic is possible, thereby enabling an improvement in manufacturing yield. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an outline of an LCD television  1  pertaining to embodiment 1; 
         FIG. 2  is a schematic perspective view of a structure of a backlight unit  5  pertaining to embodiment 1; 
         FIG. 3A  is a sectional view showing a structure of a lamp  20  pertaining to embodiment 1, and  FIG. 3B  shows a contact portion between heat dissipaters  32  and  34  and an end surface of a glass bulb  21 ; 
         FIG. 4  is a schematic perspective view of a backlight unit  100  pertaining to embodiment 2, where one part thereof has been cut away to show an interior view; 
         FIGS. 5A ,  5 B, and  5 C show an exemplary lighting circuit  160  included in the backlight unit  100 , where  FIG. 5A  shows the lighting circuit  160 , and  FIGS. 5B and 5C  show connections between lamps La in the lighting circuit  160 ; 
         FIG. 6  is an enlarged sectional view of an end of a lamp  120  pertaining to embodiment 2; 
         FIG. 7  is an enlarged sectional view of an end of a lamp  200  pertaining to embodiment 3; 
         FIG. 8  shows a melted solder  222  in a fuse  220 ; 
         FIG. 9  shows a variation of embodiment 3; 
         FIG. 10  shows a relationship between a lamp current Ila and an electrode temperature T; 
         FIG. 11  is an enlarged view showing an end of a lamp  300  pertaining to variation 1; 
         FIG. 12  shows a contact portion between a heat dissipater and an end surface of a glass bulb; 
         FIG. 13  is an enlarged view showing an end of a lamp  310  pertaining to variation 2; 
         FIG. 14  is an enlarged view showing the end of the lamp  310  pertaining to variation 2; 
         FIG. 15  shows the contact portion between a heat dissipater and an end surface of a glass bulb; 
         FIG. 16  is an enlarged view showing an end of a lamp  320  pertaining to variation 3; 
         FIG. 17  is an enlarged view showing an end of a lamp  340  pertaining to variation 4; 
         FIG. 18  shows a structure of a heat dissipater  343 ; 
         FIG. 19A  shows a heat dissipater  360  of variation 4-1, 
         FIG. 19B  shows a heat dissipater  370  of variation 4-2, and 
         FIG. 19C  shows a heat dissipater  380  of variation 4-3; 
         FIG. 20  is an enlarged sectional view of an end of a lamp pertaining to variation 5; 
         FIG. 21  is a perspective view of a covering  420  pertaining to variation 6; 
         FIG. 22A  shows a lighting circuit  440 , and  FIG. 22B  shows connections between lamps La in the lighting circuit  440 ; and 
         FIG. 23  shows an outline of a lamp  500  pertaining to variation 8. 
     
    
    
     DESCRIPTION OF THE CHARACTERS 
     
         
         
           
               1  liquid crystal display (LCD) television 
               3  liquid crystal screen unit 
               5  backlight unit 
               10  housing 
               20  cold cathode fluorescent lamps (CCFL) 
               21  glass bulb 
               22  glass tube 
               28 ,  30  electrodes 
               28 A,  30 A electrode main bodies 
               28 B,  30 B lead wires 
               32 ,  34  heat dissipaters 
               44 ,  46  glass beads 
           
         
       
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Cold cathode fluorescent lamps (hereinafter, referred simply as “lamps”), backlight units and LCD apparatuses pertaining to embodiments of the present invention are described below with reference to the drawings. Note that the drawings of the present invention are schematic diagrams for facilitating understanding of the structure of the backlight units and the lamps, and do not show actual dimensions or proportions. 
     Embodiment 1 
     1. Structure of LCD Television 
       FIG. 1  shows an outline of an LCD television  1  pertaining to embodiment 1. 
     The LCD television  1  shown in  FIG. 1  is one example of an LCD apparatus of the present invention, and is a 32-inch LCD television or the like. The LCD television  1  includes a liquid crystal screen unit  3  and a backlight unit  5 . 
     The liquid crystal screen unit  3  includes a color filter substrate, liquid crystals, a TFT substrate, and a driving module, etc. (not depicted), and forms a color image in accordance with an external image signal. 
     2. Structure of Backlight Unit 
     Following is a description of the structure of the backlight unit  5 . 
       FIG. 2  is a schematic perspective view showing the structure of the backlight unit  5  pertaining to embodiment 1. In order to show the internal structure, a portion of a front panel  16  has been cut away. 
     The backlight unit  5  includes, for example, a plurality of (for example, fourteen) cold cathode fluorescent lamps (hereinafter referred to as “lamps”)  20 , a housing  10  that stores the lamps  20  and includes an opening, the front panel  16  that covers the opening in the housing  10 , and a lighting apparatus  50  that lights the lamps  20  (omitted in  FIG. 2 , shown in  FIGS. 1 and 5A ,  5 B, and  5 C). 
     The housing  10  is made from, for example, polyethylene terephthalate (PET) resin, and includes a rectangular bottom  10   a , and four side walls  10   b ,  10   c ,  10   d , and  10   e  that are vertically arranged on the edges of the rectangular bottom  10   a . A metal such as silver has been vapor deposited on an inner surface of the housing to form a reflective surface. 
     Note that the housing  10  may be constituted from, for example, a metallic material such as aluminum or SPCC, instead of a resin. Also, instead of providing the vapor-deposited metal film, a reflective sheet, which is formed from PET resin to which calcium carbonate, titanium dioxide or the like has been added to raise a reflectivity thereof, may be adhered to the side walls and bottom of the housing. 
     Also, the opening of the housing  10  is covered by the translucent front panel  16  that is formed by laminating a diffusion plate  13 , a diffusion sheet  14 , and a lens sheet  15 , such that foreign substances such as dust and dirt cannot enter the housing. 
     The diffusion plate  13  is, for example, composed of polymethyl methacrylate (PMMA) resin, and is arranged so as to block the opening of the housing  10 . The diffusion sheet  14  is composed of, for example, polyester resin, and diffuses and scatters light that is emitted from the lamps  20 . The lens sheet  15  is, for example, an acrylic resin sheet and a polyester resin sheet attached together, and aligns the light in a normal direction of the lens sheet  15 . The diffusion plate  13 , the diffusion sheet  14 , and the lens sheet  15  cause the light emitted by the lamps  20  to radiate evenly forward from the entire surface (light-emitting face) of the front panel  16 . 
     The lamps  20  are fluorescent lamps that use cold-cathode type electrodes, and in the present embodiment, as shown in  FIG. 2 , fourteen lamps  20  are arranged such that central axes thereof conform to a lengthwise direction of the housing (shown in the drawing as the Y direction). However, the lamps may also be arranged such that central axes thereof conform to the width direction (the X direction) of the housing  10 . 
     3. Structure of the Lamp 
     Following is a description of the structure of the lamps  20 . 
       FIG. 3A  is a sectional view showing the structure of one of the lamps  20  pertaining to the present embodiment, and  FIG. 3B  shows the contact portion between heat dissipaters  32  and  34  and an end surface of a glass bulb  21 . 
     The lamp  20  includes the glass bulb  21 , formed by sealing both ends of a straight-tube cylindrical glass tube  22 , electrodes  28  and  30  that have been sealed to ends  21   a  and  21   b  of the glass bulb  21 , and the heat dissipaters  32  and  34  provided on portions of the electrodes  28  and  30  outside of the glass bulb  21 . 
     As shown in  FIG. 3A , current is supplied to the electrodes  28  and  30  from feeders  40  and  42 . Also, note that if, for example, both the ends  21   a  and  21   b  of the glass bulb are sealed with use of glass beads  44  and  46  described later, the glass bulb  21  includes the glass beads  44  and  46  in addition to the glass tube  22 . If the ends of the glass tube are pinch sealed, the glass bulb  21  only includes the glass tube  22 . 
     The glass tube  22  is composed of, for example, borosilicate glass, and a section (horizontal section) taken along a surface perpendicular to the axis is substantially circular. Note that the glass tube  22  is not limited to borosilicate glass; lead glass, lead-free glass, soda glass, or the like may also be used. This enables improvement of an in-dark start characteristic of the lamp. Specifically, the above glass contains a large amount of an alkali metal oxide typified by sodium oxide (Na 2 O), and when sodium oxide is used, for example, the sodium component elutes into an interior surface of the glass bulb as time passes. Since sodium has a low electronegativity, the sodium that elutes into the interior surface of the glass bulb (does not have a protective film) is thought to contribute to an improvement in the in-dark start characteristic of the lamp. 
     For example, when the alkali metal oxide is sodium oxide, a content ratio between 5 mol % and 20 mol % inclusive is preferable. If the alkali metal oxide comprises less than 5 mol %, the in-dark start time becomes longer, and if over 20 mol %, prolonged use causes problems such as darkening (browning) of the glass bulb leading to reduced brightness, and a decline in the strength of the glass bulb. 
     Also, using lead-free glass is preferable in consideration of environmental protection. However, there are cases in the manufacturing process of lead-free glass in which lead is included as an impurity. Therefore, lead-free glass is defined as also including glass which includes an impurity level of lead that is less than or equal to 0.1 wt %. 
     Furthermore, the cross sectional shape of the glass tube  22  is not limited to a circle, and may be another shape, such as an oval. 
     A discharge medium such as mercury or a rare gas (argon, neon, or the like) has been sealed inside the glass bulb  21  at a predetermined pressure. Note that the discharge medium is filled to a negative pressure. 
     A phosphor layer  23  has been formed on an inner surface of the glass bulb  21 . 
     The phosphor layer  23 , which is constituted from rare-earth phosphor or the like, converts ultraviolet radiation radiated from the mercury to a predetermined wavelength of visible light. As examples of rare-earth phosphors, red (Y 2 O 3 :Eu 3+ ), green (LaPO 4 :Ce 3+ ,Tb 3+ ) and blue (BaMg 2 Al 16 O 27 :Eu 2+ ) can be used. 
     Note that the phosphor layer  23  is not limited to the above structure. For example, phosphor that absorbs 313-nm ultraviolet radiation such as red phosphor (YVO 4 :Eu 3+ ), green phosphor (BaMg 2 Al 16 O 27 :Eu 2+ ) and blue phosphor (BaMg 2 Al 16 O 27 :Eu 2+ , Mn 2+ ) may be included. 
     As described above, using phosphor that absorbs 313-nm ultraviolet radiation for 50 wt % or more of the total phosphor weight almost entirely prevents leakage of 313-nm ultraviolet radiation from the lamp, and use of this lamp in the backlight unit can prevent degradation of the resin or the like used in the front panel  16  due to ultraviolet radiation (see  FIG. 2 ). In particular, polycarbonate (PC) resin, when used for the diffusion plate  13  of the front panel  16 , is more easily influenced by 313-nm ultraviolet radiation to degrade and discolor than acrylic resin. Accordingly, including phosphor that absorbs 313-nm ultraviolet radiation in the phosphor layer  23  enables maintaining the attributes of the backlight unit for a long time, even when the backlight unit uses a PC resin diffusion plate. 
     The definition used here for “absorbing 313-nm ultraviolet radiation” is having a 313-nm excitable wavelength spectrum intensity of 80% or more when the intensity of an approximately 254-nm excitation wavelength spectrum is 100% (the excitation wavelength spectrum is a spectrum in which an excitation wavelength and a light intensity when a phosphor is excited over a range of wavelengths is plotted). In other words, phosphor that absorbs 313-nm ultraviolet radiation is phosphor that can convert 313-nm ultraviolet radiation to visible light. 
     Examples of phosphor that absorbs 313-nm wavelength ultraviolet radiation are as follows. 
     Blue phosphor: BaMg 2 Al 16 O 27 : Eu 2+ , Sr 10 (PO 4 ) 6 Cl 2 :Eu 2+ , (Sr, Ca, Ba) 10 (PO 4 ) 6 Cl 2 :Eu 2+ , Ba 1−x−y Sr x Eu y Mg 1−z Mn z Al 10 O 17  (However, x, y, and z are numbers that satisfy the conditions that 0≦x≦0.4 and 0.07≦y≦0.25, and 0.1≦z≦0.6, and it is especially desirable for z to be such that 0.4≦z≦0.5). 
     Green phosphor: BaMg 2 Al 16 O 27 :Eu 2+ , Mn 2+ , MgGa 2 O 4 :Mn 2+ , CeMgAL 11 O 19 :Tb 3+ . 
     Red phosphor: YVO 4 :Eu 2+ , YVO 4 :Dy 3+ , (green and red emission). 
     Note that instead of using only one type of emission color, a mixture using phosphor of a different compound may be used. For example, the following phosphors may be used: for blue, BAM only; for green, LAP (does not absorb 313 nm) and BAM:Mn 2+ ; for red, YOX (does not absorb 313 nm) and YVO 4 :Eu 3+ . 
     As shown in  FIG. 3A , the electrodes  28  and  30  include electrode main bodies  28   a  and  30   a  that are shaped like tubes each having one closed end, and lead wires  28   b  and  30   b , each of which has one end that is fixed to the closed end of one of the electrode main bodies. Note that the electrodes  28  and  30  have the same structures. 
     The electrode main bodies  28   a  and  30   a  here are hollow, and an emitter that is an electron-emitting substance is applied to an inner surface of the tube. For example, a metal such as nickel, niobium, tantalum, molybdenum, and tungsten is used to form the electrode main bodies  28   a  and  30   a , and a carbonate such as barium, strontium, or calcium, an alkali metal oxide, or an alkaline earth metal is used as the emitter. 
     The lead wires  28   b  and  30   b  are composed of a material such as tungsten, and are thinner than the tube-shaped electrode main bodies  28   a  and  30   a . As shown in  FIG. 3A , attachment of the electrodes  28  and  30  to the ends  21   a  and  21   b  of the glass bulb  21  is achieved by, for example, sealing the outer circumference of the glass beads  44  and  46  to the inner circumference of the ends  21   a  and  21   b  of the glass bulb  21  while the lead wires  28   b  and  30   b  are inserted into the through-holes  44   a  and  46   a  of the glass beads  44  and  46  in a way that forms an airtight seal. 
     Similar in shape to the electrode main bodies  28   a  and  30   a , the heat dissipaters  32  and  34  are tubes having end walls  32   a  and  34   a  on one side, and ends of the lead wires  28   b  and  30   b  have been inserted into through-holes that exist in a central part of the end walls  32   a  and  34   a . Note that tungsten or the like can be used to form the heat dissipaters  32  and  34 , similarly to the lead wires  28   b  and  30   b.    
     When viewed externally along an extending direction of the lead wires  28   b  and  30   b , outer surfaces of the end walls  32   a  and  34   a  of the heat dissipaters  32  and  34 , as shown in  FIG. 3B , surround the lead wires  28   b  and  30   b  and contact the end surface of the glass bulb  21  (although this contact is actually with the end surfaces of the glass beads  44  and  46 , the glass beads  44  and  46  are considered to be included in the glass bulb  21 ). Specifically, when these contact portions are externally viewed along the extending direction of the lead wire axis (hereinafter referred to as an axial direction), the end walls  32   a  and  34   a  of the heat dissipaters  32  and  34  touch the end surfaces  21   c  and  21   d  of the glass bulb  21  around the outer circumference (in a circumferential direction) of the lead wires  28   b  and  30   b  (substantially around an entirety of the outer surface of the end walls  32   a  and  34   a  of the heat dissipaters  32  and  34 ). 
     Note that setting an outer diameter D 2  of the heat dissipater  32  and  34  smaller than an outer diameter D 1  of the glass bulb  21  enables the entire range of the outer surface of the end walls  32   a  and  34   a  of the heat dissipaters  32  and  34  to be substantially in contact with the end surfaces  21   c  and  21   d  of the glass bulb  21 . However, in view of the dissipation characteristic of the heat dissipaters  32  and  34  when the lamps are lit, although the dissipation area becomes larger and the dissipation characteristic improves in proportion to increasing the outer diameter D 2  of the heat dissipaters  35  and  36 , when the heat dissipaters are larger than the lamps  20 , the backlight unit also becomes thick. Accordingly, the outer diameter D 2  of the heat dissipaters  32  and  34  is preferably substantially less than or equal to the outer diameter D 1  of the glass bulb  21 . 
     4. Effects 
     (1) Breakage of Lead Wires 
     The lamps  20  having the above structure prevent deformation and breakage of the lead wires  28   b  and  20   b  even when the heat dissipaters  32  and  34  touch the walls, etc. of the housing  10 , for example, during attachment of the lamps  20  to the housing  10  since the end walls  32   a  and  34   a  of the heat dissipaters  32  and  34  provided on one end of the lead wires  28   b  and  30   b  are in contact with the end surfaces  21   c  and  21   d  of the glass bulb  21 . 
     (2) Dissipation Characteristic 
     When lit, the lamps  20  described above can transfer heat generated in the lead wires  28   b  and  30   b  and the electrode main bodies  28   a  and  30   a  from the lead wires  28   b  and  30   b  to the heat dissipaters  32  and  34  via the glass beads  44  and  46 , and can also transfer heat directly from the lead wires  28   b  and  30   b  to the heat dissipaters  32  and  34 . For this reason, the heat quantity transferred to the heat dissipaters  32  and  34  is large compared to a case in which for example, as in conventional technology, the heat dissipater is separated from the glass bulb, enabling suppressing thermal elevation in the electrode main bodies  28   a  and  30   a.    
     Also, since the heat dissipaters  32  and  34  are circular and can dissipate heat not only from an outer peripheral surface but also from an inner peripheral surface, the heat dissipaters  32  and  34  can efficiently dissipate the heat that passed through the lead wires  28   b  and  30   b . Furthermore, since the outer diameter D 2  of the heat dissipaters  32  and  34  is substantially equal to the outer diameter D 1  of the glass bulb  21 , the above effects can be obtained by the lamp  20  without an increase in size. 
     Embodiment 2 
     In embodiment 1, current is supplied to the lamp  20  via contact between the feeders  40  and  42 , the heat dissipaters  32  and  34 , and the lead wires  28   b  and  30   b . In embodiment 2, a feeder is provided at each end of the glass bulb, and mounting to the lamp housing and feeding to the lamp housing is performed by a socket method. 
     1. Structure of Backlight Unit 
       FIG. 4  is a schematic perspective view of a backlight unit  100  pertaining to embodiment 2, where one part thereof has been cut away to show an interior view. 
     Similarly to embodiment 1, the backlight unit  100  includes a housing  110 , a front panel (not depicted), a plurality of lamps  120 , and a lighting circuit  160  (see  FIG. 5 ) that lights the plurality of lamps  120 . 
     As shown in  FIG. 4 , the housing  110  includes sets of U-shaped lamp holders  130  and  132  that are provided on a bottom  110   a  of the housing  110  and that are disposed in correspondence with the mounting positions of the lamps  120 , and the lighting circuit  160  (see  FIG. 5 ) that is, for example, mounted externally to the housing  110 , for lighting the lamps  120  connected to the lamp holders  130  and  132 . Note that the lamps  120  have feeders  124  and  126  provided on external circumferences of ends of the glass bulb  121  and receive a power supply from the lamp holders  130  and  132  via the feeders  124  and  126 . 
     The lamp holders  130  and  132  have been formed from folded sheets of a conductive material such as stainless steel or phosphor bronze. The lamp holders  130  ( 132 ) include clamp plates  130   a  and  130   b  ( 132   a ,  132   b ) and a connection piece  130   c  ( 132   c ) that connects the lower edges of the clamp plates  130   a  and  130   b  ( 132   a ,  132   b ). 
     Depressions conforming to the contours of the feeders  124  and  126  of the lamps  120  are provided in the clamp plates  130   a ,  130   b ,  132   a , and  132   b . When the feeders  124  and  126  of lamps  120  are fit into the depressions, the plate spring effect of the clamp plates  130   a ,  130   b ,  132   a , and  132   b  holds the lamps  120  in the lamp holders  130  and  132  and electrically connects the lamp holders  130  and  132  to the feeders  124  and  126 . 
     Note that in order to suppress a corona discharge from occurring when the lamps are lit, a width DL of holding portions of the lamp holders  130  and  132  is set to enable only holding areas of the lamps  120  that include the externally provided feeders  124  and  126 . 
       FIGS. 5A ,  5 B, and  5 C show an exemplary lighting circuit  160  included in the backlight unit  100 , where  FIG. 5A  shows the lighting circuit  160 , and  FIG. 5B  shows connections between lamps La in the lighting circuit  160 . 
     The lighting circuit  160  shown in  FIG. 5  supplies power to the lamps  120  provided in the backlight unit  100  via the lamp holders  130  and  132 . 
     Here, the lamp holders  130  and  132  hold the plurality of lamps  120  in substantially parallel rows at a predetermined interval, and the lamp holders  132 , which hold the feeders  126  on one side of two neighboring lamps  120  (in  FIGS. 5B and 5C , the feeder  126  for the lamps La 1  and La 2 , or La 7  and La 8 ; etc.), are electrically connected to each other. 
     As a result, two straight tube-shaped lamps La 1  and La 2 , for example, enable formation of a pseudo-curved tube (U-shaped tube). Along with halving the number of inverters needed, this pseudo-curved tube, in comparison to a lamp having a conventional curve, also reduces luminance irregularities in the longitudinal direction (the axial direction, left and right of the housing interior) of the lamps  120 , and furthermore prevents breakage of the attachment portions, etc. of the lamps  120 , and enables one-touch mounting or removal of the lamps  120 . 
     Also, since the straight tube-shaped lamps  120  that have electrodes  28 , described later, on both ends are arranged vertically for example, the electrodes  28  acting as sources of heat are not concentrated on one side, which prevents temperature differences between right and left sides of the housing interior, as a result suppressing luminance irregularities of the backlight unit  100  caused by mercury vapor pressure in the lamps  120 . 
     Furthermore, as shown in  FIG. 4 , insulation plates  134 , composed of polycarbonate, have been disposed between the lamp holders  130  and  132  and the housing  110  to insulate the lamp holders  130  and  132  and the housing  110  from each other. 
     Also, the lamp holders  132  that are connected to the feeders  126  of the lamps La 1  and La 2  and to the feeders  126  of the lamps La 7  and La 8  in  FIG. 5B  have been individually soldered to a metal plate  132   d.    
     Note that although each lamp holder  132  is made up of multiple pieces, is U-shaped, and is individually soldered to the metal plate  132   d  in correspondence with one of the lamps  120 , the present invention is not limited to this. The clamp plates  132   a  and  132   b  may be formed from one sheet as a single piece, according to a conventional method. 
     Following is a description of an exemplary lighting circuit  160 . 
     As shown in  FIG. 5A , the lighting circuit  160  includes a direct current power source (V DC ), switch elements Q 1  and Q 2  and capacitors C 2  and C 3  that are connected to the direct current power source (V DC ), step-up transformers T 1  and T 2  (or T 7  and T 8 ) that are connected to the connection between the switch elements Q 1  and Q 2  and the connection between the capacitors C 2  and C 3 , and an inverter control IC that supplies a gate signal for switching the switch elements Q 1  and Q 2  alternately ON and OFF. 
     Also, as shown in  FIG. 5B , a series resonance circuit is formed by leakage inductance on the secondary side of the transformer and parasitic capacity occurring between transformer output and an inner surface of the housing  110 , and between transformer output and the lamps, and the lighting circuit  160  supplies a sinewave current having a phase difference of substantially 180 degrees to the two connected lamps La 1  and La 2 . 
     Note that although in  FIG. 5B , a plurality of lamps La are connected such that the lamp holders  132  holding the feeders  126  at one end of the two adjacent lamps La 1 , La 2  are mutually connected to form a pseudo-curved tube (U-shaped tube), the present invention is not limited to this. The lamp holders  132  may be connected such that, as shown in  FIG. 5C , the feeders  124  on one side of a pair of adjacent lamps La or the feeders  126  on the other side are alternately connected. Among the plurality of arranged lamps La (for example, the adjacent lamp pairs La 1  and La 2 , La 2  and La 3 , La 3  and La 4 , La 9  and La 10 , La 10  and La 11 , or La 11  and La 12 , and for ease of understanding, the following description will be limited to the adjacent lamp pairs La 1  and La 2 , La 2  and La 3 , and La 3  and La 4 ), the lamp holders  130  and  132  may form a zigzag alignment in the following order. First the feeders  126  of the adjacent lamp pair La 1  and La 2  are interconnected, then the feeders  124  of the adjacent lamp pair La 2  and La 3  are interconnected, and next the feeders  126  of the adjacent lamp pair La 3  and La 4  are interconnected. 
     Note that in this case, as shown in  FIG. 5C , the lamp holders  132  on the feeders  126  of the lamps La 1 , La 2 , and so on are connected to each other via the metal plate  132   d . Also, the lamp holders  130  on the feeders  124  of the lamps La 2 , La 3 , and so on are connected to each other via a metal plate  130   d.    
     As well as enabling a further reduction in the number of inverters, this structure enables harness processing to be executed merely by using a zigzag alignment of lamp holders  130  and  132 . In other words, a reduction in harness processing is possible since the lamp holders  130  and  132  do not require harness processing from the lighting circuit. 
     2. Structure of the Lamp 
       FIG. 6  is an enlarged sectional view of an end of a lamp  120  pertaining to embodiment 2. Note that constituent elements having similar structures to embodiment 1 have been given the same reference notations. 
     Similarly to embodiment 1, the lamp  120  includes the glass bulb  21 , an electrode  28 ( 30 ) that has been attached at an end  21   a ( 21   b ) of the glass bulb  21 , a covering  125  ( 125 ) that covers the end  21   a  ( 21   b ) of the glass bulb  21  and extends further outward than the end  21   a ( 21   b ) of the glass bulb  21 , and a heat dissipater  128  ( 128 ) in the feeders  124  and  126  that is provided around a lead wire  28   b ( 30   b ) extending from an end surface  21   c ( 21   d ) of the glass bulb  21 . 
     The heat dissipater  128  ( 128 ), which is a conductive material, fits in the space enclosed by the covering  125 , and electrically connects the feeder  124  ( 126 ), the covering  125 ( 125 ) and the lead wire. 
     Note that although only one side of the lamp  120  (the feeder  124  side) is depicted in  FIG. 6 , an electrode similar to the one in embodiment 1 has also been provided on the other side, and similarly to the depicted side, and the feeder  126  including the covering  125  and the heat dissipater  128  has also been provided on the other end. Also, as in embodiment 1, mercury, rare gases and the like are sealed inside the glass bulb  21 , and a phosphor layer  23  has been formed on the inner surface of the glass bulb  21 . 
     Similarly to embodiment 1, the electrode  28 ( 30 ) includes an electrode main body  28   a ( 30   a ) and a lead wire  28   b ( 30   b ). The heat dissipater  128 ( 128 ) is in an inner portion of the covering  125 ( 125 ), and has been formed by filling solder or the like in an area that spans from the end surface  21   c ( 21   d ) of the glass bulb  21  to an outward edge of the covering  125 ( 125 ) in an axial direction of the lamp. Note that the heat dissipater  128 ( 128 ) is formed with the lead wire  28   b ( 30   b ) embedded substantially in a center thereof, and an end  128   a ( 128   a ) thereof is in contact with the end  21   c ( 21   d ) of the glass bulb  21 . 
     As described above, a conductive material (solder) is used for the heat dissipaters  128 , and when the lamps  120  are mounted in the lamp holders  130  and  132 , the covering  125  receives a feed from the lamp holders  130  and  132 , as a result of which current flows to the electrode main bodies  28   a  and  30   a . Note that a material (metal) having good conductivity is used since, in this way, the covering  125  must conduct a current. 
     3. Effects 
     (1) Breakage of the Lead Wire 
     Similarly to embodiment 1, since the lead wire  28   b  is buried in the heat dissipater  128  ( 128 ) and has surface contact with the end face  21   c ( 21   d ) of the glass bulb  21 , breakage, etc. of the lead wire  28   b  ( 30   b ) is reduced in the lamps  120  pertaining to embodiment 2 even when the heat dissipaters come into contact with the walls of the housing  110 . 
     (2) Heat Dissipation Characteristic 
     When the lamps  120  described above are lit, heat generated in the lead wire  28   b ( 30   b ) and the electrode main bodies  28   a ( 30   a ) is transferred from the lead wires  28   b ( 30   b ) to the heat dissipater  128 ( 128 ) via the glass beads  44 ( 46 ), and heat can also be transferred from the lead wires  28   b ( 30   b ) directly to the heat dissipater  128 ( 128 ), and furthermore can be transferred from the heat dissipater  128 ( 128 ) and the glass beads  44 ( 46 ) to the covering  125 ( 125 ). 
     Thus, a greater amount of heat is transferred to the heat dissipater  128 ( 128 ) and the covering  125 ( 125 ) than in conventional technology, in which the heat dissipater is apart from (not touching) the glass bulb, thereby enabling commensurately better suppression of thermal elevation in the electrode main body  28   a ( 30   a ). 
     Embodiment 3 
     Although the lamp  120  of embodiment 2 includes the glass bulb  21 , the electrode  28 ( 30 ), and the feeders  124  and  126 , another member may be included as well. 
     The following describes a case in embodiment 3 in which a fuse is included as an additional member. 
     1. Structure 
       FIG. 7  is an enlarged sectional view of an end of a lamp  200  pertaining to embodiment 3. 
     The lamp  200  includes a glass bulb  202 , an electrode  204 , a covering  207 , a heat dissipater  208 , and a fuse  220 . 
     Here, the electrode  204  includes an electrode main body  212  and a lead wire  214 , and the lead wire  214  is composed of a large-diameter part  214   a  and a small-diameter part  214   b  that is thinner than the large-diameter part  214   a . The large-diameter part  214   a  is formed in an area of the lead wire  214  from a connection between the electrode main body  212  and the lead wire  214  to an outer end of a sealing part  202   a  of the glass bulb  202 . Furthermore, the small-diameter part  214   b  is formed in an area of the lead wire  214  that extends externally from the glass bulb  202 . 
     A fuse  220  has been mounted to an outer end of the lead wire  214 , that is, to the outer end of the small-diameter part  214   b . Note that the lead wire  214  and the fuse  220  are electrically connected. 
     As shown in  FIG. 7 , in the fuse  220 , a pair of terminal lead wires  224  and  226  are connected via a solder  222 , and the terminal lead wire  224  is connected to the lead wire  214  in a substantially straight line. Note that the lead wire  214  and the lead wire  224  have been connected by soldering or the like. 
     A rosin  228  coats the solder  222  and a connection between the solder  222  and the terminal lead wires  224  and  226 . Also, an insulation case  230  hermetically seals the solder  222 . The insulation case  230  includes a tube  232  and lids  234   a  and  234   b  that block the openings of both sides of the tube  232 . 
     Here, the terminal lead wires  224  and  226  are constituted from nickel wires for example, and a composition of the solder  222  is, for example, Sn: 96.5%, Ag: 3.0%, and Au: 0.5% solder. The melting point of the solder is approximately 220° C. The tube  232  is made of a ceramic material for example, and the lids  234   a  and  234   b  are made from resin (epoxy resin), for example. 
     Similarly to embodiment 2, a metallic sleeve is used as the covering  207  to cover an end ( 202   a ) of the glass bulb  202  so that an end thereof protrudes outward. 
     Except for the insulation space  236 , a space enclosed by the part of the covering  207  that protrudes from the end ( 202   a ) of the glass bulb  202  is filled by a heat dissipater  208  that is made of solder or the like. According to this structure, the heat dissipater  208  ensures power conductivity between the terminal lead wire  226  and the feeder  206 , and the feeder  206  is formed as a result. 
     Note that the insulation space  236  is provided in order to prevent electricity from flowing from the small-diameter part  214   b  of the lead wire  214  and the terminal lead wire  224  to the covering  207  via the heat dissipater  208  and also to channel current to the solder  222  in the fuse  220 . 
     The solder  222  melts down when the current flowing therein exceeds a predetermined value and becomes overcurrent, thus breaking the feed (power distribution) from the feeder  206  to the electrode  204 . 
       FIG. 8  shows the solder  222  that has melted down in the fuse  220 . 
     As shown in  FIG. 8 , when an overcurrent flows into the solder  222 , the solder  222  melts down and divides into a solder  222   a  and a solder  222   b . The divided solder  222   a  and  222   b  are still covered by the rosin  228 . 
     Since the rosin  228  is an insulating material, the terminal lead wire  224  and the terminal lead wire  226  are electrically insulated from each other. Even if a voltage is applied to the feeder  206 , current will not flow into the lead wire  214 , since the feeder  206  and the lead wire  214  are electrically insulated from each other. 
     Also, ozone production is prevented, since a discharge (corona discharge) is not generated between the solders  222   a  and  222   b  after meltdown due to being coated by the insulating rosin  228 . 
     Even in a case in which the solders  222   a  and  222   b  are not covered by the rosin  228  and are exposed, and a discharge occurs between the solders  222   a  and  222   b , the oxygen in the air does not become ozone due to the discharge since the space around the junctions between the terminal lead wires  224  and  226  and the solders  222   a  and  222   b  has been sealed by the insulation case  230 . Accordingly, ozone production is prevented. 
     Note that although in embodiment 3, the covering  207  is a sleeve shape, another shape such as a cap shape may be used. The following briefly describes this as a variation of embodiment 3. 
       FIG. 9  shows a variation of embodiment 3. 
     Similarly to embodiment 3, a lamp  250  of the variation includes the glass bulb  202 , the electrode  204 , a covering  253 , the heat dissipater  208 , and the fuse  220 . 
     As shown in  FIG. 9 , the covering  253  has a cap shape, and includes a tube part  253   a  and a bottom part  253   b  that blocks one end of the tube part  253   a . In the present variation, the terminal lead wire  254  that is not connected to the lead wire  214  in the fuse  220  has been fitted into a through-hole in the bottom part  253   b . Note that the terminal lead wire  254  and the covering  253  may be either electrically connected or not electrically connected. 
     2. Dissipation Effect 
     The inventors performed a validation test concerning the effect of the heat dissipater. Specifically, the inventors performed a test with use of a lamp in which a lead wire  350  (outer lead part  354 ) of an electrode shown in  FIG. 17  that is described later as variation 4 has been extended to an end surface of a heat dissipater  343 . 
     Following is a description of the basic structure of the lamp used in the test. The outer diameter R of a glass bulb  342  is 3.0 mm, and the total length of the lamp is 417 mm. The lead wire  350  of the electrode includes an inner lead part  352  whose outer diameter is 1.0 mm, and the outer lead part  354  whose outer diameter is 0.8 mm. The total length of the covering  345  is 7.5 mm, and a heat dissipater  343  is provided in all the remaining space enclosed by the covering  345  that is covering the glass bulb  342 . 
     Note that an electrode main body  348  is made of nickel, and in the lead wire  350 , the inner lead part  352  is made of tungsten, and the outer lead part  354  is made of nickel. The heat dissipater  343  is constituted from solder, and the covering  345  is made of an iron-nickel alloy. 
     In the test, the amount that the covering  345  extends from the end surface of the glass bulb  342 , that is, “L” of  FIG. 17 , was either 0.5 mm, 1.0 mm, or 1.5 mm, and one of each type of lamp was manufactured. With use of these three lamps, the relationship between the lamp current and the temperature of the electrode main body was measured and the effect of the heat dissipater was checked. 
       FIG. 10  shows a relationship between lamp current Ila and electrode temperature T. 
     In  FIG. 10 , the result of a lamp having an “L” of 0.5 mm is designated by a circle “O”, the result of a lamp having an “L” of 1.0 mm is designated by a square “□”, and the result of a lamp having an “L” of 1.5 mm is designated by a triangle “Δ”. Note that in order to check the above heat dissipation effect, the test was similarly performed on a lamp that does not include a sleeve or a heat dissipater and whose outer lead part length is 1.5 mm, and this result is depicted in  FIG. 10  as “x ref”. 
     In the lamps that are provided with a heat dissipater, and in the lamp that is not provided with a covering or a heat dissipater, the electrode temperature T rises in accordance with an increase in the lamp current Ila. However, in comparison to the lamp that is not provided with a covering or a heat dissipater, the lamp that is provided with a heat dissipater clearly has a lower rise in the electrode temperature T in accordance with the increase in the lamp current Ila (a smaller temperature gradient). 
     Also, when the lamps including heat dissipaters are compared to each other, the rise in temperature in accordance with an increase in lamp current Ila is substantially the same. The lack of a large difference between the heat dissipation effect of the lamps is thought to be due to the fact that there is no change in the contact area between the heat dissipater and the glass bulb, even if the amount of protrusion (L) of the covering from the end of the glass bulb changes within a range of L values in the test. 
     The lamp pertaining to the present invention is preferably used such that when lit, the lamp current Ila is in a range between 5 mA and 12 mA inclusive. The reason for this is that the effect of the heat dissipater cannot be obtained (that is, the dissipation characteristic is the same as a lamp that does not include a heat dissipater) if the lamp current Ila is less than 5 mA. On the other hand, if the current Ila is greater than 12 mA, the temperature of the electrode rises too high, incurring a risk that the solder constituting the heat dissipater will melt down. 
     Note that the lamp current Ila is even more preferably in a range between 5 mA and 9.5 mA inclusive. A case in which the lamp current Ila is below 5 mA has the same issue as above. On the other hand, if the lamp current Ila is greater than 9.5 mA, the electrode temperature Twill reach or exceed 130° C., depletion of the electrode main body will become extreme due to sputter, and the lamp efficiency will decrease. 
     Although described based on the above embodiments, the present invention is of course not limited to the concrete examples of such embodiments. Variations such as the following are also included in the present invention. 
     Variations 
     1. The Heat Dissipater 
     (1) Shape 
     In the embodiments, the end surface of the heat dissipater on the glass bulb side is flat. This is because the end surface of the glass bulb (glass bead) is flat and substantially orthogonal to the central axis of the glass bulb, and the end surface of the heat dissipater is flat for the purpose of establishing surface contact with the flat end surface of the glass bulb. Note that the reason for establishing surface contact is to enlarge the contact area between the heat dissipater and the glass bulb, and to prevent deformation of the lead wire. 
     However, the end surface of the glass bulb may have a shape other than the flat shape orthogonal to the central axis of the glass bulb. In such a case, the end surface of the heat dissipater on the glass bulb side, rather than having a flat shape, preferably conforms to the shape of the glass bulb end surface, in order to establish surface contact between the heat dissipater and the glass bulb end surface. Following is a description of variations pertaining to shapes of the heat dissipater. 
     (1-1) Variation 1 
       FIG. 11  is an enlarged view showing an end of a lamp  300  pertaining to variation 1. Note that one end side of the lamp  300  is described in variation 1, and the structure of the other end is similar to the one end side. 
     Similarly to embodiments 1 to 3, the lamp  300  of variation 1 includes a glass bulb  302 , the electrode  28  and a heat dissipater  304 . 
     Similarly to embodiments 1 to 3, the electrode  28  includes an electrode main body  28   a  and a lead wire  28   b , and the lead wire  28   b  is sealed in an end of the glass bulb  302  via a glass bead  306 . Here also, the glass bulb  302  is composed of a glass tube  308  and the glass bead  306 . 
     Although the glass bulb  302  is basically the same as the glass bulb of the embodiments 1 to 3, the glass bead  306  differs from the shape described in embodiments 1 to 3, and has a shape of an arc protruding outwardly. Accordingly, the end face  302   a  of the glass bulb  302  has an arc shape similar to the end surface shape of the glass bead  306 . 
     Similarly to embodiments 1 to 3, the heat dissipater  304  is provided around the lead wire  28   b  of the electrode  28  outside of the glass bulb  302 . 
       FIG. 12  shows a contact portion between the heat dissipater and the end surface of a glass bulb. 
     As shown in  FIG. 11 , the heat dissipater  304 , is substantially columnar, and the end on the glass bulb  302  side is depressed inwards in an arc shape that has a smaller curvature than the arc shape of the end surface  302   a  of the glass bulb  302 . Also, as shown in  FIG. 12 , the heat dissipater  304  has contact (surface contact) with the end surface  302   a  of the glass bulb  302  (the contact part in  FIG. 12 ) on the circumference of a predetermined radius (having a predetermined width) having the lead wire  28   b  as a center. 
     Specifically, the heat dissipater  304 , when viewed externally along the extending direction of the lead wire  28   b  is in contact with the entire circumference (while surrounding the lead wire  28   b ) of the end surface  302   a  of the glass bulb  302  around the lead wire  28   b . In particular, the portions having surface contact, as shown in  FIG. 12 , when viewed externally along the extending direction of the lead wire  28   b , include apexes of a virtual triangle X 2  of which the lead wire  28   b  is located in a center. 
     This structure enables suppressing deformation of the lead wire  28   b , even in a case in which, for example, the heat dissipater  304  comes into contact with a surrounding member when mounting the lamp  300  in the housing. Needless to say, the structure also enables efficient transfer of the heat generated in the lit lamp from the electrode  28  to the heat dissipater  304 . 
     The attachment of the heat dissipater  304  to the glass bulb  302  is achieved by, for example, when the end of the glass bulb  302  has been slightly melted by heating, pressing the heated portion into a mold that is depressed inwardly in an arc having a predetermined curvature, thereby forming the end shape of the glass bulb  302  into a predetermined arc. Then, a lead wire aperture (hole) in the pre-manufactured heat dissipater  304  is heat-fitted around the lead wire  28   b  and the end surface  304   a  of the heat dissipater  304  is pushed against the glass bulb  302 . 
     Note that in variation 1, as shown in  FIG. 12 , the heat dissipater  304  has surface contact with the end surface  302   a  of the glass bulb  302 , and for example, even if the heat dissipater is in linear contact with an entire circumference of the end of the glass bulb around the lead wire, a similar dissipation effect is obtained, though inferior to the dissipation effect in variation 1. Specifically, the amount of heat transferred to the heat dissipater from the electrode in this case is smaller than a case in which the heat dissipater has surface contact with the glass bulb  302  as in the above variation 1, but greater than a case in which the heat dissipater is not in contact with the glass bulb. 
     (1-2) Variation 2 
       FIGS. 13 and 14  are enlarged views showing an end of a lamp  310  pertaining to variation 2. Note that one end side of the lamp  310  is described in variation 2, and the structure of the other end is similar to the one end side. 
       FIG. 13  shows the end of the glass bulb sectioned along a surface perpendicular to a direction of pinch sealing when viewed from the direction of pinch sealing.  FIG. 14  shows the end of the glass bulb sectioned along a surface parallel to a direction of pinch sealing when viewed from a direction perpendicular to the direction of pinch sealing. 
     Similarly to embodiments 1 to 3 and variation 1 (hereinafter to be referred to collectively as “embodiments, etc.”) the lamp  310  pertaining to variation 2, similarly to embodiments 1 to 3 and variation 1 (hereinafter to be referred to collectively as “embodiments and variations”) includes a glass bulb  312 , the electrode  28  and a heat dissipater  314 . 
     Similarly to the embodiments, etc., the electrode  28  includes an electrode main body  28   a  and a lead wire  28   b . Pinch-sealing an end of the glass tube  316  while the electrode main body  28   a  is inserted into the glass bulb  312  seals the glass bulb  312 . Note that here, the glass bulb  312  is composed of the glass tube  316 . 
     Since the end  316   a  of the glass tube  316  is pinch sealed (the sealed portion is designated as “ 316   b ”), the end shape of the glass bulb  312  is different from the embodiments etc. described above. 
     The heat dissipater  314  is on a portion of the lead wire  28   b  of the electrode  28  that is outside the glass bulb  312 , and is provided so as to contact an end surface  316   c  of the glass bulb  312  (the glass tube  316 ). 
     The heat dissipater  314  is substantially columnar, and the end surface  314   a  on the glass bulb  312  side conforms to the shape of the end surface  316   c  of the glass bulb  312 , and a portion corresponding to the sealed part  316   b  of the glass bulb  312  is depressed. 
       FIG. 15  shows contact portions between the heat dissipater and the end surface of a glass bulb. 
     As shown in  FIG. 15 , the heat dissipater  314  is in surface contact with the end surface  316   c  of the glass bulb  312  and the sealed part  316   b , while facing (in the drawing, facing up and down) and sandwiching the sealed part  316   b  of the glass bulb  312 . Also, as shown in  FIG. 15 , the portions in surface contact, when viewed externally along the extending direction of the lead wire  28   b , surround the lead wire  28   b . In other words, the portions that have surface contact include the apexes of a virtual square X 3  of which the lead wire  28   b  is located in a central inner portion. 
     This structure enables suppressing deformation of the lead wire  28   b , even in a case in which, for example, the heat dissipater  314  comes into contact with a surrounding member when mounting the lamp to the housing. Needless to say, the structure also enables efficient transfer of the heat generated in the lit lamp from the electrode  28  to the heat dissipater  314 . 
     For example, the heat dissipater  314  can be realized by disposing, on the end of the glass bulb  312 , a ring-shaped mold whose inner diameter is equal to the outer diameter of the heat dissipater  314 , and filling the mold with melted solder. 
     (1-3) Other variations 
     The glass bulb of variation 1 or 2 can also be used in the lamp of embodiment 2. In this case, any one of the heat dissipaters described in embodiments 2 or 3 etc., or in variation 1 can be used. Furthermore, the feeder of embodiment 2 or 3, etc. may be provided at the end of the glass bulb in variations 1 and 2. 
     (2) Relationship to the Lead Wire 
     Although the heat dissipater of the embodiments, etc. is separate from the lead wire, the heat dissipater and the lead wire may also be integrally formed as one piece. For example, a heat dissipater integrally formed using the same material as the lead wire may have the same structure as the heat dissipater described in the embodiments and variations etc., and be formed at an end of the lead wire that is on an opposite side from the electrode main body. Note that when the lead wire and the heat dissipater are separately formed, the same material can be used for both, or a different material may be used for each. 
     (3) Contact Between the Heat Dissipater and the Glass Bulb 
     In the embodiments, etc., the contact portions between the heat dissipater and the glass bulb are such that, when viewed externally along the extending direction of the lead wire, either surface contact or linear contact is achieved between the heat dissipater and the glass bulb, and the contact portion includes the apexes of a virtual polygon of which the lead wire is located in an inner center, so that the lead wire is not likely to deform even when something comes into contact with the end of the lamp. However, as long as deformation of the lead wire is merely suppressed in some way, the heat dissipater and the glass bulb do not need to have surface or linear contact with each other. 
     For example, the heat dissipater may touch three or more points on the end surface of the glass bulb where the lead wire is located internally on the end surface of the glass bulb, and the lead wire may be located within a virtual polygon (a polygon having three or more sides) that connects the points of contact. Note that the contact portions between the heat dissipater and the glass bulb of the embodiments and variations, needless to say, include the three points mentioned above. 
     2. Electrode 
     Although the lead wire of the electrode in embodiment 2 is substantially rod-shaped (unstepped), other shapes may be used. Another shape is described as variation 3. 
       FIG. 16  is an enlarged view showing an end of a lamp  320  pertaining to variation 3. 
     The structure of the lamp  320  is basically the same as the lamp  120  of embodiment 2, and includes the glass bulb  21 , an electrode  322 , a heat dissipater  128 , and the covering  125 . 
     The electrode  322  includes an electrode main body  324  and a lead wire  326  that is connected to the electrode main body  324 . The lead wire  326  includes an inner lead part  327 , an outer lead part  328 , and a bulge  329  located between the inner lead part  327  and the outer lead part  328 . 
     The inner lead part  327  includes a portion that is attached to the glass bead  44  and a portion that extends from the glass bead  44  into the glass bulb  21 . The outer lead part  328  is constituted from a portion in which the central axis of the inner lead part  327  is extended from the bulge  329  to an exterior of the glass bulb  21 . 
     The bulge  329  has an outer diameter that is at least equal to the outer diameter of the inner lead part  327 . The bulge  329  is formed by, for example, soldering together the inner lead part  327  and the outer lead part  328 . 
     Providing the bulge  329  on the lead wire  326  of the electrode  322  enables keeping a constant dimension from the bulge  329  to the electrode main body  324 . Specifically, reducing the gap between the bottom of the electrode main body  324  and the inner surface of the facing glass bead  44  (for example, to approximately 0.5 mm) enables lengthening an effective emission length of the lamp. 
     Note that although the bulge  329  is formed from the same nickel material as the outer lead part  328 , the formation is not limited to this. The bulge  329  may be an Fe—Ni alloy, a Cu—Ni alloy, Dumet (dual metal), etc. 
     The inner lead part  327  has a substantially circular cross section, and has, for example, a total length of 3 mm and a wire diameter of 0.8 mm. Also, the inner lead part  327  has been inserted into a through-hole  44   a  and sealed therein so that an end on the bulge  329  side contacts (or substantially contacts) the end surface of the glass bead  44 . The end opposite to the outer lead part  328  side has been joined to an outside surface of the bottom  322   a  of the electrode main body  322  in a substantially central position. 
     The outer lead part  328  and the bulge  329  are protrusions that protrude in a central axial direction from the outer surface of the glass bulb  21  and are joined to the covering  125  via the heat dissipater  128 . This structure constitutes the feeder  124 . The horizontal section of the outer lead part  328  and the bulge  329  is substantially circular, the total length of both in the central axial direction is, for example, 1 mm, and the central axis of the outer lead part  328  substantially matches the central axis of the end of the glass bulb  21 . 
     In view of the total size of the lamp, the total length of both the outer lead part  328  and the bulge  329  in the central axial direction is, preferably, 1 mm or less. Also, in view of parts cost and breakage of the portion where the glass bead  44  and the inner lead part  327  are sealed (hereinafter referred to as the “sealed portion”), the outer diameter of the bulge  329  is preferably between 1.5 times and 4 times the outer diameter of the inner lead part  327 . 
     As described above, it is preferable for the outer diameter of the glass bulb  21  to be within the range of 1.8 mm to 6.0 mm in order to make the lamp  320  longer and thinner, and in the lamp  320  having this size, the total length in the central axial direction of the outer lead part  328  and the bulge  329  preferably does not project out from the heat dissipater  128 , in other words, is preferably a length that is buried within the heat dissipater  128 . 
     This structure can prevent bending of the outer lead part  328  and breakage of the sealed portion between the glass bead  44  and the inner lead part  327 , when the outer lead part  328  comes into contact with a surrounding member. Also, if contact occurs with the backlight housing or a socket or the like in the backlight housing when mounting the lamp  320  to the backlight unit, the risk of bending the outer lead part  328  and of breaking the glass bead  44  due to stress exerted on the outer lead part  328  at that time is small. 
     Also, if the outer lead part  328  comes into contact with an external part before being covered by the heat dissipater  128 , since both ends of the glass bulb  21  absorb the force exerted on the bulge  329 , this structure prevents leaks resulting from breakage of, for example, the glass bead  44 , to which the inner lead part  327  is sealed. 
     3. Covering, Heat Dissipater and Electrode 
     In embodiment 2, the heat dissipater  128  fills the sleeve-shaped covering  125  such that the electrode  28  is buried within, and the electrode includes one lead wire. However, other structures may be used. Another structure is described below as another variation. 
     (1) Variation 4 
       FIG. 17  is an enlarged view showing an end of a lamp  340  pertaining to variation 4. 
     Similarly to the embodiments etc., the lamp  340  pertaining to variation 4 includes a glass bulb  342 , an electrode  344 , a heat dissipater  343  and a covering  345 . 
     The cross section of the glass bulb  342  is circular, and has an outer diameter of 4 mm, an inner diameter of 3 mm, and a thickness of 0.5 mm, for example. An end of the glass bulb  342  is a sealed part  342   a  that has been pinch-sealed for attachment of the electrode  344 . 
     Note that a phosphor layer has been formed on an inner surface of the glass bulb  342 , and mercury, rare gases and the like are enclosed in the interior. 
     The electrode  344  is a so-called hollow-type electrode, includes an electrode main body  348  and a lead wire  350 , and is sealed to the sealed part  342   a  of the glass bulb  342 . 
     The electrode main body  348  is made of nickel (Ni), and has the shape of a bottomed tube. Note that the material of the electrode main body  348  is not limited to nickel, and for example, niobium (Nb), tantalum (Ta), or molybdenum (Mo) may be used. 
     The electrode main body  348  has, for example, a total length of 5.2 mm, an outer diameter of 2.7 mm, an inner diameter of 2.3 mm, and a thickness of 0.2 mm. The electrode  344  is arranged so that the central axis of the electrode main body  348  is substantially aligned with the central axis of an end of the glass bulb  21 , and the interval between the outer circumferential surface of the electrode main body  348  and the inner circumferential surface of the glass bulb  342  is substantially uniform across the entire area of the outer circumference of the electrode main body  348 . 
     The interval between the outer circumferential surface of the electrode main body  348  and the inner surface of the glass bulb  342  is, specifically, 0.15 mm. When the interval is this small, electrical discharge cannot occur in this narrow space, and thus occurs only in the interior of the electrode main body  348 . Accordingly, sputtered material dispersed by the electrical discharge does not easily attach to the inner surface of the glass bulb  342 , thereby extending the life of the lamp  340 . 
     At the same time, since the space is narrow and electrons and the like cannot pass behind the electrode  348 , or in other words, cannot flip around to the lead wire  350  side at the time of discharge, the lead wire  350  is not readily heated by electron sputter and the like. 
     Note that the interval between the outer circumferential surface of the electrode main body  348  and the inner surface of the glass bulb  342  does not need to be 0.15 mm. However, it is preferable for the interval to be 0.2 mm or below in order to prevent discharge from entering the interval. 
     The lead wire  350  is a continuous wire composed of an inner lead part  352  made of tungsten (W) and an outer lead part  354  made of nickel that readily attaches with use of solder or the like. The junction between the inner lead part  352  and the outer lead part  354  substantially matches and becomes one surface with the outer surface of the glass bulb  342 . Thus, the inner lead part  352  is located farther inward than the outer surface of the glass bulb  342 , and the outer lead part  354  is located farther outward than the outer surface of the glass bulb  342 . 
     The inner lead part  352  has a substantially circular cross section, and has, for example, a total length of 3 mm and a wire diameter of 0.8 mm. The end of the inner lead part  352  on the side nearest to the outer lead part  354  is sealed to the sealed part  342   a  of the glass bulb  342 , and the end on the side farthest from the outer lead part  354  is joined to a substantially central part of the outer surface of the bottom of the electrode main body  23 . 
     The heat dissipater  343  is inside the sleeve-shaped covering  345 , and has been provided in the remaining space from the end surface of the glass bulb  342  to the outer edge of the covering  345 . The heat dissipater  343  is constituted from solder, and has been pre-shaped (in a shape conforming to the remaining space). 
     In the heat dissipater  343 , a through-hole  343   a  for the outer lead part  354  of the electrode  344  has been formed at a position corresponding to the central axis of the outer lead part  354 , and the outer lead part  354  has been inserted into the through-hole  343   a.    
     The outer lead part  354  has been joined to the heat dissipater  343  by a projection that protrudes from an outer surface of the glass bulb  342  along the central axial direction. The outer lead part  354  has a total length of 1 to 10 mm, and is for example 2 mm, and the central axis of the outer lead part  354  is substantially in alignment with the central axis of the glass bulb  342 . 
     The covering  345  has a sleeve shape and is composed of an iron-nickel alloy. 
     If the total length of the outer lead part  354  exceeds 10 mm, a crack could form on the sealed part  342   a  of the glass bulb  342  due to stress from the outer lead part  354 , and in order to achieve the function of the outer lead part  354 , the total length must be at least 1 mm. Also, a cross section of the outer lead part  354  is substantially circular, and the wire diameter is thinner than that of the inner lead unit  352 , for example, 0.6 mm. 
     Note that in variation 4 also, the feeder  346  has been formed by connecting the covering  345  to the lead wire  350  via the heat dissipater  343 . 
     In the above structure, an end of the glass bulb  342  has been directly inserted into the covering  345 , and the outer lead part  354  and the covering  345  are electrically connected via the heat dissipater  343  that exists in the remaining space of the covering  345 . Even if the heat dissipater  343  comes into contact with the glass bulb  342  and stress is exerted on the glass bulb  342  due to the difference in coefficient of thermal expansion between the heat dissipater  343  and the glass bulb  342 , and while the lamp is lit, cracks do not readily form in the glass bulb  342 , since unlike patent document 1, the heat dissipater is not covering the side surface of the glass bulb. 
     Also, when the length L between an outward end surface of the feeder  346  (covering  345 ) shown in  FIG. 17  and the end surface of the glass bulb  342  increases, the surface area of the feeder  346  (the covering  345 ) increases and the dissipation characteristic improves. Specifically, the length L is preferably, for example, longer than the outer diameter R of the glass bulb  342 . 
     Following is a description of a manufacturing method for the lamp  340 . 
     First, the glass bulb  342 , the heat dissipater  343 , and the covering  345  are prepared. 
       FIG. 18  shows a structure of the heat dissipater  343 . 
     As shown in  FIG. 18 , the heat dissipater  343  is columnar, and one end thereof has a depression conforming to the shape of the end surface of the glass bulb  342 , and the through-hole  343   a  has been formed in a position corresponding to the central axis of the heat dissipater  343 . 
     Following is a description of a manufacturing method for the heat dissipater  343 . 
     First, columnar solder is formed. At this time, the outer diameter of the columnar solder substantially equals the inner diameter of the covering  345 . Then, the columnar-shaped through-hole  343   a  that has a diameter substantially equal to the wire diameter of the outer lead part  354  is formed along the central axis of the columnar solder (the columnar solder axis and the through-hole axis substantially match). Furthermore, one end surface of the columnar solder is (mechanically) processed (forming step) to conform to the end surface of the glass bulb. In this way, the heat dissipater  343  can be acquired. 
     Following is a description of a process for mounting the covering  345 . 
     After the end of the glass bulb  342  ( 342   a ) has been inserted from one end of the covering  345  to the middle thereof, for example by heating and inserting the covering  345  (heat-fitting), the outer lead part  354  of the electrode  344  is inserted into the through-hole  343   a  of the heat dissipater  343  while the heat dissipater  343  is inserted into the covering  345  until the end surface  343   b  of the heat dissipater  343  comes into contact with the end surface of the glass bulb  342 . 
     Lastly, heat is applied to a substantially central portion of the covering  345  in the axial direction (a position corresponding to where the glass bulb  342  and the heat dissipater  343  are in contact with each other). Then, the heat melts a portion of the heat dissipater  343 , which is made of solder, that is near the end of the glass bulb  342 , thereby attaching (affixing) the heat dissipater  343  and the glass bulb  342  together. 
     At this time, the end surface  343   b  located on the glass bulb  342  side of the heat dissipater  343  has a shape conforming to the end surface of the glass bulb  342 , and, since the end of the heat dissipater  343  on the glass bulb side (at least including the end surface) has been melted, solder enters a narrow gap between the end surface of the glass bulb  342  and the covering  345 , thereby forming contact between the end surface  343   b  of the heat dissipater  343  and the end surface of the glass bulb  342  (contact process). 
     In the lamp  340 , obtained by the above manufacturing method, the glass bulb  342  is inserted directly into the covering  345 , and the outer lead part  354  and the covering  345  are electrically connected via the heat dissipater  343  in the remaining space in the covering  345 . 
     For this reason, since contact between the heat dissipater  343  and the glass bulb  342 , if occurring, only occurs on the end surface of the glass bulb  342 , even if stress is exerted on the glass bulb  342  due to a difference in coefficient of thermal expansion between the heat dissipater  343  and the glass bulb  342 , cracks do not readily form in the glass bulb  342 . 
     Also, since the heat dissipater  343  is provided so as to be in close contact with an end surface of the glass bulb  342 , the heat released from the electrode main body  348  is conducted to the covering  345  via the glass bulb  342 , the lead wire  350 , the heat dissipater  343 , etc., and ultimately dissipates from the covering  345  into the atmosphere, thus achieving a high degree of heat dissipation. 
     Note that the heat dissipater  343  can also be formed by pouring melted solder into a metal cast in the shape of the heat dissipater  343 , i.e. by casting. 
     (2) Other Examples 
     Aside from variation 4 described above, other examples in which the heat dissipater is provided in the feeder are also possible. 
     (2-1) Variation 4-1 
       FIG. 19A  shows a heat dissipater  360  of variation 4-1. 
     As shown in  FIG. 19A , the heat dissipater  360  pertaining to variation 4-1 is composed of a body  362  and a solder  364 . The body  362  is, for example, composed of copper, and is shaped as a column having a through-hole  362   a  in a substantially central position, which is provided for insertion of a lead wire. 
     The solder  364  is joined to one end surface of the body  362  (in  FIG. 19A , the left side end surface). The solder  364  is disc-shaped, and has the through-hole  364   a  in the center thereof, and a surface  364   a  on the opposite side, which is the joint surface between the solder  364  and the body  362 , has a shape corresponding to the shape of the end surface of the glass bulb. 
     Following is a brief description of the attachment of the heat dissipater  360  and the sleeve-shaped covering to the glass bulb. 
     First the covering is attached to the end of the glass bulb with use of, for example, heat-fitting. 
     Next, the heat dissipater  360  is inserted into the covering until a surface  364   b  of the solder  364  touches the end surface of the glass bulb. At this time, since the surface  364   b  of the solder  364  has a shape that substantially conforms to the end surface of the glass bulb, the solder  364 , that is, the heat dissipater  360 , comes into close contact with the end surface of the glass bulb (or the portion to be attached expands). 
     In this state, heat is applied from the end surface of the body  362  and the outer circumference of the covering until the solder  364  reaches a melting temperature. The application of heat is stopped when the solder  364  melts, and the solder cools naturally. 
     Attaching the covering and the heat dissipater  360  to the glass bulb with use of this method enables improvement of the dissipation characteristic, since melted solder enters the narrow space formed between the end surface of the glass bulb and the covering, and the heat dissipater  360  is attached to the glass bulb with no space therebetween. 
     The structure shown in  FIG. 19A  has the advantage that heat for melting the solder is easily conducted to the solder  364 , which is a junction to the glass bulb, by applying heat to the body  362  when the glass bulb and the heat dissipater are joined in the manufacturing process. 
     (2-2) Variation 4-2 
       FIG. 19B  shows the heat dissipater  370  of variation 4-2. 
     As shown in  FIG. 19B , the heat dissipater  370  pertaining to variation 4-2 includes a body  372  and a solder film  374 . Similarly to variation 4-1, the body  372  has a columnar shape, and one side surface  372   a  (in  FIG. 19B , the left side) of the body  372  has a shape corresponding to the shape of the glass bulb end surface. 
     The solder film  374  is applied to the end surface  372   a  of the body  372 . Since the solder film  374  is applied to the end surface  372   a  of the body  372  at a substantially even thickness, the surface  374  of the solder film  374   a  has a shape conforming to the end surface of the glass bulb. Note that the attachment of the heat dissipater  370  and the sleeve-shaped covering to the glass bulb is similar to variation 4-1 above. 
     Similarly to the structure shown in  FIG. 19A , the structure shown in  FIG. 19B  has the advantage that heat for melting the solder is easily conducted to the solder  374 , which is a junction to the glass bulb, by applying heat to the body  372  when the glass bulb and the heat dissipater  370  are joined in the manufacturing process. Also, merely by applying the solder film  374  at an even thickness to the end surface  372   a  of the body  372 , and pressing the body  372  on the glass bulb end side when the solder film  374  melts, the surface  374   a  of the solder  374  conforms to the end surface of the glass bulb, and the contact area between the heat dissipater and the glass bulb can be increased. Of course, the manufacturing process can also be simplified. 
     (2-3) Variation 4-3 
       FIG. 19C  shows a heat dissipater  380  of variation 4-3. 
     As shown in  FIG. 19C , the heat dissipater  380  pertaining to variation 4-3 includes a body  382  and a solder film  384 . Similarly to variation 4-1, the body  382  is a copper column, and one end surface of the body  382  (in  FIG. 19C , the left side) and the side surface thereof are covered by the solder film  384 . The surface  384   b  of the solder film  384  that is to touch the end surface of the glass bulb is pre-fabricated (formed) to conform to the glass bulb end surface. 
     The attachment of the heat dissipater  370  and the sleeve-shaped covering to the glass bulb is similar to variation 4-1, and an effect similar to the effect described in variations 4-1 and 4-2 can be obtained by the structure shown in  FIG. 19C . 
     (3) Variation 5 
     Although in variation 4, as shown in  FIG. 17 , the lamp  340  is formed with use of the sleeve-shaped feeder  346  and the heat dissipater  343  that is made of solder, the lamp may have another structure. Another structure is described below as variation 5. Note that in the following description, a “feeder terminal” is composed of a covering and a heat dissipater. 
       FIGS. 20A and 20B  are enlarged sectional views of an end of a lamp pertaining to variation 5. 
     As shown in  FIG. 20A , a feeder terminal  400  pertaining to variation 5 is composed of a covering  402  and a heat dissipater  404 , and is attached to the end of the glass bulb  342 . The heat dissipater  404  includes a conductor plate  406  and a solder  405 . 
     The conductor plate  406  is composed of, for example, the same iron nickel alloy composing the covering  402 . The outer diameter of the conductor plate  406  is substantially equal to the inner diameter of the covering  402 , and a surface  406   a  touching the glass bulb  342  conforms to the end surface of the glass bulb  342 . 
     Following is a description of a process for mounting the feeder terminal  400  to the glass bulb  342 . First, the end of the glass bulb  342  is inserted into the covering  402  to a predetermined length. Next, the outer lead part  354  is inserted through the through-hole  406   b  in the conductor plate  406 , and then the solder  405  is inserted into the covering  402  until the conductor plate  406  comes into contact with the end surface of the glass bulb  342 . 
     The glass bulb  342  is disposed such that the axis thereof is disposed vertically, and solder in a melted state (hereinafter referred to as “melted solder”) (this becomes the solder  405 ) flows in the space that is separated by the inner wall of the covering  402  and the conductor plate  406 . Since the covering  402  and the conductor plate  406  have a high coefficient of thermal conductively and reach a high temperature due to heat from the melted solder, the melted solder flows into the narrow space formed between the covering  402  and the conductor plate  406 . 
     This structure improves the efficiency of thermal conductivity from the glass bulb  342  to the conductor plate  406  since the conductor plate  406  is in contact with the glass bulb  342 . Accordingly, the heat emitted from the electrode main body  348  is released into the atmosphere from the covering  402  and the solder  405  which connect with the conductor plate  406 , as a result, increasing the lamp&#39;s dissipation characteristic. 
     Although not described in the present variation, for example, a plurality of through-holes may be formed in the conductor plate  406 . Since the melted solder flows into the through-holes during the forming process, the seal between the conductor plate  406  and the end of the glass bulb  342  improves, and the thermal conductivity effect from the glass bulb  342  to the conductor plate  406  increases. Note that the through-holes preferably have a diameter that is 3 mm or less and that for example, a plurality of through-holes are formed, each of which is approximately 0.5 mm. 
     Also, the covering  402  and the conductor plate  406  shown in  FIG. 20A  may be soldered together as shown in  FIG. 20B . The covering  410  may include a tube and a conductor plate integrally formed as one piece, and the feeder  412  may be constituted from such covering  410  and the solder  408 . Note that in this case, the covering  410  corresponds to the heat dissipater pertaining to the present invention. 
     (4) Variation 6 
     Although the covering of the above embodiments and variations mainly has a sleeve shape, other shapes may also be used. Another shape is described below as variation 6. 
       FIG. 21  is a perspective view of a covering  420  pertaining to variation 6. 
     The covering  420  pertaining to the present variation is, for example, a flat sheet that has been rounded to form a shape such that the ends do not meet. In other words, the tube has a slit  422  along the lengthwise direction in a portion of the circumferential direction (thus a cross section taken perpendicular to a lengthwise direction forms a C-shape). 
     Providing a feeder terminal on the end of the glass bulb with use of the covering  420  is thought to have the effect of suppressing the formation of air bubbles in the gap between the glass bulb and the heat dissipater, since air bubbles are emitted from the slit  422  when connecting the covering  420  and the lead wire with use of a heat dissipater composed of, for example, solder. Note that if a sleeve-shaped feeder not having a slit is used, the air bubbles are sucked out in a vacuum atmosphere or the like in the gap. 
     4. Backlight Unit 
     (1) Structure 
     The backlight units described in the above embodiments store the lamps  20  and  120  in the housings  10  and  110 , and are direct-type backlight units in which the lamps  20  and  120  directly illuminate the liquid crystal image units  11 . However, other types of backlight units may be used. Specifically, an edge type that provides a lamp on an edge of a light guide plate, where light from the lamps reflects off of the light guide plate to irradiate a liquid crystal panel may be used. Note that lamps in an edge-type backlight unit may be straight tubes, or may have an L-shape that conforms to abutting edges of the light guide plate. 
     (2) Variation 7 
     Although in the lighting circuit  160  of embodiment 2, two adjacent lamps have a phase difference of substantially 180 degrees, for example, the same phase of sine-wave current may be provided to both adjoining lamps. This case is described below as variation 7. 
       FIG. 22A  shows a lighting circuit  440 , and  FIG. 22B  shows connections of the lamps La in the lighting circuit  440 . 
     The lighting circuit  440  has a substantially similar structure to the lighting circuit  160  of embodiment 2. As shown in  FIG. 22A , the lighting circuit  440  includes a direct current power source (V DC ); switch elements Q 1 , Q 2  and capacitors C 2 , C 3  that are connected to the direct current power source (V DC ); step-up transformers T 1  and  2 T 2  (or step-up transformers T 7  and  2 T 8 ) that connect the connections between the switch element Q 1  and the switch element Q 2 , the condenser C 2  and the condenser C 3 ; and an inverter control IC that supplies a gate signal for flipping switch elements Q 1 , Q 2  ON and OFF alternately. 
     In the lighting circuit  160  of embodiment 2, the secondary-side transformer connection orientations of the two step-up transformers  2 T 2  and  2 T 8  differ from each other. This enables supplying sine-wave currents having the same phase to two adjacent lamps. 
     Following is a description of the lamp connection with reference to  FIG. 22B . 
     In variation 7, similarly to embodiment 2, a feeder is provided on the end of a glass bulb, and attachment to the lamp housing and feeding is performed with use of a socket method. Here, since the lamps, lamp holders, and feeders are the same as embodiment 2, the same reference notations are used in the following description. 
     A plurality of lamps  120  are connected and held substantially parallel to each other by lamp holders  130  and  132  with a predetermined interval therebetween. Also, the lamp holder  132  that holds the feeder  126  on one side of two adjacent lamps  120  (in  FIG. 22B , the feeder  126  of lamps La 1  and La 2  or La 7  and La 8 ) has been connected to the grounded side. 
     Also, the lamp holders  130  that connect and hold feeder  124  on the other side of two adjacent lamps  120  (in  FIG. 22B , the feeder  124  of lamps La 1 , La 2 , La 7 , and La 8 ) are connected on the high-voltage side of the lighting circuit  440 . 
     Since the same effect as embodiment 2 can be obtained by this structure, a voltage phase difference is substantially zero degrees, voltage-potential differences having the same potential are applied to two adjacent lamp holders  130 , and the interval between two adjacent lamps  120  can be smaller than in a case in which the voltage phase difference is substantially 180 degrees. 
     Note that in order to make the voltage phase difference substantially zero degrees and to further reduce harness processing, the lamp holders  132  that connect and hold the feeder  126  on one side of the plurality of lamps La 1  through La 8 , for example, are all grounded. As shown in  FIG. 22B , this grounding is performed by soldering each one of the U-shaped lamp holders  132  to the metal substrate  445 . 
     5. Lamp Shape, Etc. 
     Although the lamps described in the embodiments are straight-tube-shaped, other shapes may be used, for example, a U-shape, a C-shape having three straight sides, or a W-shape. 
     The outer diameter of the lamps is preferably 5 mm or less. This is because, the thinner the lamp, the thinner the electrode becomes, and the higher the electrode temperature rises when the lamp is lit. In particular, this is because if the outer diameter is 5 mm or less, reduction in the life of the lamp and the decrease in lamp efficiency becomes significant, thereby requiring an improvement in the dissipation characteristic of the electrode. 
     Also, although the cross section of the lamp in the embodiments, etc. is substantially circular, other shapes may be used. A lamp having another shape is described below as variation 8. 
       FIG. 23  shows an outline of a lamp  500  pertaining to variation 8. 
     As shown in  FIG. 23 , the lamp  500  includes a glass bulb  508  formed by sealing both ends  504  and  506  of a glass tube  502  whose cross section is oval, electrodes  28  and  30  that are respectively attached to the ends  504  and  506  of the glass bulb  508 , and heat dissipaters  32  and  34  provided on the electrodes  28  and  30  of an external portion of the glass bulb  508 . 
     Note that the electrodes  28  and  30  and the heat dissipaters  32  and  34  of the lamp  500  have a similar structure to embodiment 1 except for the glass bulb  508 . 
     The glass tube  502  that constitutes the glass bulb  508  has a cross section that is oval, as shown in  FIG. 23C . As shown in  FIG. 23B , the cross section of both ends  504  ( 506 ), is substantially circular. The central portion here refers to at least a light-extracting portion (a flattened portion in an area between the tips of the electrode main bodies  28   a  and  30   a  arranged at the ends of the glass bulb  508 ) in the positive column emission portion of the glass bulb  508  (substantially in the area where the positive column is emitted). Note that the phosphor layer  509  has been formed in a part corresponding to the light-extracting portion of the glass bulb  508 . 
     The measurements of the lamp  500  are given below. The total length L 1  of the lamp  500  is 705 mm, the length Da of the positive column emission portion is approximately 680 mm, the lengths Db and Dc of circular portions on the electrode part sides are approximately 12 mm each, and the outer circumferential surface area of the positive column emission portion is approximately 105 cm 2 . 
     Also, as shown in  FIG. 23C , the substantial oval has an external minor axis ao of 4.0 mm, an internal minor axis ai of 3.0 mm, an external major axis bo of 5.8 mm, and an internal major axis bi of 4.8 mm. Also, as shown in  FIG. 23B , the substantially circular tube outside diameter ro is 5.0 mm, and the tube inner diameter ri is 4.0 mm. 
     Flattening the cross section of the light-extracting portion of the glass bulb  508  suppresses an extreme rise in temperature of the coldest temperature by making the outer circumference surface area greater than in a conventional straight tube lamp. Furthermore, the external minor axis ai that has a flat shape is shorter than in a conventional straight tube lamp that has a tube inner diameter similar to the internal major axis bi, thereby enabling effectively keeping a short distance from a center of a positive column plasma space to an inner wall of a tube. Thus, this structure suppresses a decrease in light emission efficiency even if the lamp current is higher than in a conventional lamp. 
     INDUSTRIAL APPLICABILITY 
     A cold cathode fluorescent lamp pertaining to the present invention can be used as a light source for thin and large-screen backlight units, and a backlight unit pertaining to the present invention can be used in thin and large-screen display apparatuses.