Abstract:
Provided is an electronic package (PG) which is made without using screws or double-sided adhesive tapes, so cost can be reduced and the manufacturing process can be made simpler. This is done by configuring the electronic package (PG) so that a backlight chassis ( 10 ) thereof includes anchoring claws ( 11 ) for fixing a mounted substrate ( 21 ) onto itself. A lighting device (backlight unit ( 49 )) and a displaying device (liquid crystal display device ( 69 )) are provided with this electronic package (PG).

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to an electronic package as a part of an electronic device, and more particularly to an electronic package that includes a chassis and a mounting board fitted to the chassis. The invention also relates to, as examples of electronic devices, illuminating devices and display devices. 
       BACKGROUND ART 
       [0002]    Liquid crystal display devices (display devices) incorporating a non-luminous liquid crystal display panel (display panel) generally also incorporate an illuminating device, such as a backlight unit, that supplies light to the liquid crystal display panel. There are many kinds of light sources for use in backlight units. For example, the backlight unit disclosed in Patent Document 1 listed below incorporates LEDs (light-emitting diodes) as a light source. 
         [0003]    As shown in  FIG. 17 , such LEDs  122  are mounted on mounting boards  121 , which are fitted to a backlight chassis  110  (the package including the backlight chassis  110  and the mounting boards  121  is referred to as the electronic package pg). 
       LIST OF CITATIONS 
     Patent Literature 
       [0000]    
       
         Patent Document 1: JP-A-2009-158193 
       
     
       SUMMARY OF INVENTION 
     Technical Problem 
       [0005]    The fitting of the mounting boards  121  to the backlight chassis  110  is achieved by use of screws  181  (see Patent Document 1, paragraph [0023]). Inconveniently, this increases the number of components, and accordingly the cost, of the backlight unit. 
         [0006]    Moreover, the manufacturing process of the backlight unit inevitably involves operation for tightening many screws  181 , complicating the manufacture of the backlight unit and resulting in a long manufacturing time. 
         [0007]    Instead of screws  181 , as shown in  FIG. 18 , double-sided adhesive tape  182  may be laid between the mounting boards  121  and the backlight chassis  110  for the fitting of the mounting boards  21  to the backlight chassis  110 . 
         [0008]    Inconveniently, however, using the double-sided adhesive tape  182  makes little difference than using screws  181  in increasing the number of components and complicating the manufacturing process (double-sided adhesive tape  182  may be used in combination with screws  181  to fit the mounting boards  121  to the backlight chassis  110 , but doing so will naturally further increase the number of components and further complicates the manufacturing process). 
         [0009]    The present invention has been made to overcome the inconveniences mentioned above, and aims to provide an electronic package, as a part of an electronic device (such as lighting devices), and the like that can be manufactured easily and at low cost. 
       Solution to Problem 
       [0010]    In an electronic package including a chassis and a mounting board fitted to the chassis, the chassis itself includes a fastening portion for fastening the mounting board. 
         [0011]    With this design, there is no need for screws or double-sided adhesive tape for fastening the mounting board to the chassis. This helps reduce the number of components of, reduce the cost of, and simplify the manufacture of the electronic package. 
         [0012]    It is preferable that the fastening portion be hook-shaped, rising from the bottom surface of the chassis and bent toward the bottom surface. 
         [0013]    This fastening portion engages with the edge of the mounting board and in addition holds the mounting board between the tip portion of the hook and the bottom surface of the chassis, thus allowing the chassis to be stably fastened to the chassis. 
         [0014]    It is preferable that, in a case where the hook-shaped fastening portion, at a rising segment which is the portion of the fastening portion rising from the bottom surface of the chassis, makes contact with the edge of the mounting board, a plurality of the fastening portion be arranged at opposite edges of the mounting board. 
         [0015]    With this design, the fastening portions not only hold the mounting board between the tip portion of the hook and the bottom surface of the chassis but also hold the mounting board itself, thus allowing the chassis to be more stably fastened to the chassis. 
         [0016]    It is preferable that the hook-shaped fastening portion include a rising segment which is the portion of the fastening portion rising from the bottom surface of the chassis and an overhanging segment which is the portion of the fastening portion crossing the rising segment and overhanging a mounting surface of the mounting board, and that a projection for increasing the pressing force against the mounting surface be formed on the overhanging segment. 
         [0017]    With this design, in a case where the mounting board is held between the overhanging segment, which is the tip portion of the hook, and the mounting board, the projection formed on the overhanging segment, if any, makes the distance between the overhanging segment and the bottom surface of the chassis shorter by the height of the projection. This increases the pressing force of the overhanging segment against the mounting surface of the mounting board, thus allowing the fastening portion to more stably fasten the mounting board to the chassis. 
         [0018]    It is preferable that the mounting board include a hole in which the projection on the overhanging segment fits. With this design, the projection on the fastening portion fits in the hole, and thereby prevents the mounting board from moving in any direction with respect to the fastening portion, hence the chassis. Thus, the fastening portion more stably fastens the mounting board to the chassis. 
         [0019]    It is preferable that the hook-shaped fastening portion be formed by cutting and raising part of the bottom surface of the chassis. With this design, there is no need for an extra member for forming the fastening portion. 
         [0020]    In addition, forming the fastening portion leaves an opening in the chassis. The opening makes it easier for outside air to enter from the outside, and thus, even when heat collects in the mounting board, the heat dissipates into outside air. 
         [0021]    To allow more outside air to enter the electronic package, it is preferable that the bottom surface of the chassis have a window to be shaped like a skeleton. 
         [0022]    In a case where heat collects in the mounting board, it is preferable that the chassis, which makes contact with the mounting board, be made of a high-heat-dissipation material such as aluminum alloy or carbon fiber-reinforced plastic. With this design, the heat collecting in the mounting board dissipates to the chassis. 
         [0023]    Giving a coarse surface to at least part of the chassis increases the area of contact with outside air, and thus promotes the dissipation of the heat collecting in the mounting board to the chassis. In particular, locating the coarse-surfaced part of the chassis on a surface of the chassis facing outward permits it to make contact with outside air outside the electronic package, and this ensures the dissipation of the heat collecting in the mounting board. 
         [0024]    Coarse-surfacing is not the only means of enhancing the dissipation of heat from the chassis. Instead, high-emissivity paint may be applied to at least part of the chassis. Particularly preferable is to locate the high-emissivity paint-applied part of the chassis on a surface of the chassis facing outward. Also with this design, the heat collecting in the mounting board dissipate via the high-emissivity paint to the chassis. 
         [0025]    The present invention encompasses lighting devices that include an electronic package as described above in combination with a light source mounted on the mounting surface of the mounting board. 
         [0026]    In such lighting devices, it is preferable that a reflective sheet covers the mounting surface, with the reflective surface of the reflective sheet facing outward and the reverse surface to the reflective surface facing the mounting surface, and that the reflective sheet have a perforation formed therein to expose only the light-exit region of the light source where the light source emits light. 
         [0027]    With this design, only the light-exit region of the light source is exposed through the perforation, and this eliminates the part of the reflective surface that absorbs light (that is, its part between the rim of the perforation and the light-exit region). Thus, less of the light from the light source is lost before being output, permitting the illuminating device to produce high-quality light free from uneven light distribution. 
         [0028]    The present invention encompasses display devices that include an illuminating device as described above in combination with a display panel which receives light from the illuminating device. 
       Advantageous Effects of the Invention 
       [0029]    With an electronic package according to the present invention, it is possible to fasten a mounting board to a chassis without using screws, double-sided adhesive tape, or the like. The electronic package thus contributes to reduced cost and a simplified manufacturing process. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0030]      FIG. 1  is an exploded perspective view of a liquid crystal display device. 
           [0031]      FIG. 2  (A) is a plan view showing part of a backlight chassis etc. included in a liquid crystal display device; (B) is a sectional view of the backlight chassis etc. shown in (A) along line A 1 -A 1 ′ as seen from the direction indicated by arrows; and (C) is a sectional view of the backlight chassis etc. shown in (A) along line B 1 -B 1 ′ as seen from the direction indicated by arrows. 
           [0032]      FIG. 3  is an exploded perspective view of LED modules and a backlight chassis to which the LED modules are fitted. 
           [0033]      FIG. 4  is a perspective view showing LED modules in the process of being fitted to a backlight chassis. 
           [0034]      FIG. 5  is a perspective view showing a backlight chassis having LED modules fitted to it. 
           [0035]      FIG. 6  is a sectional view of a hook. 
           [0036]      FIG. 7  is a plan view of a mounting board having a hole and an overhanging segment having a projection seen through the hole. 
           [0037]      FIG. 8  is a plan view of a mounting board having holes. 
           [0038]      FIG. 9  is a perspective view of a backlight chassis having rectangular windows formed in it to be shaped like a skeleton. 
           [0039]      FIG. 10  is a plan view of a backlight chassis having rectangular windows formed in it to be shaped like a skeleton. 
           [0040]      FIG. 11  is a plan view of a backlight chassis having rhombic windows formed in it to be shaped like a skeleton. 
           [0041]      FIG. 12  is a plan view of a backlight chassis having circular windows formed in it to be shaped like a skeleton. 
           [0042]      FIG. 13  is a plan view of a backlight chassis having triangular and trapezoid windows formed in a mixed fashion in it to be shaped like a skeleton. 
           [0043]      FIG. 14  is a three-view diagram composed of a plan view of the rear side of the bottom surface of a backlight chassis and side views of the side surface of the backlight chassis as seen from two sides. 
           [0044]      FIG. 15  (A) is a plan view showing part of a backlight chassis etc. included in a liquid crystal display device; (B) is a sectional view of the backlight chassis etc. shown in (A) along line A 2 -A 2 ′ as seen from the direction indicated by arrows; and (C) is a sectional view of the backlight chassis etc. shown in (A) along line B 2 -B 2 ′ as seen from the direction indicated by arrows. 
           [0045]      FIG. 16  is graphs of front luminance plotted against position on a sectional view of a backlight unit. 
           [0046]      FIG. 17  is an exploded perspective view of a conventional backlight unit. 
           [0047]      FIG. 18  is an exploded perspective view of a conventional backlight unit. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiment 1 
       [0048]    An embodiment of the present invention will be described below with reference to the accompanying drawings. For convenience&#39; sake, hatching and reference signs are occasionally omitted, in which case any other relevant drawings are to be referred to. Conversely, also for convenience&#39; sake, hatching is occasionally used other than in sectional views. A solid black dot appearing on arrows indicates the direction perpendicular to the plane of paper. 
         [0049]      FIG. 1  is an exploded perspective view of a liquid crystal display device.  FIG. 2A  is a plan view showing part of a backlight chassis  10  etc. included in the liquid crystal display device  69  (more specifically, a plan view of the backlight chassis  10  having, stacked on its bottom surface  10 B, LED modules MJ and a reflective sheet  43 ).  FIG. 2B  is a sectional view of the backlight chassis  10  etc. shown in  FIG. 2A  along line A 1 -A 1 ′ as seen from the direction of arrows, and  FIG. 2C  is a sectional view of the backlight chassis  10  etc. shown in  FIG. 2A  along line B 1 -B 1 ′ as seen from the direction of arrows. 
         [0050]    As shown in  FIG. 1 , the liquid crystal display device  69  includes a liquid crystal display panel  59 , a backlight unit (illuminating device)  49  which supplies light to the liquid crystal display panel  59 , and a housing HG (a front housing HG 1  and a rear housing GH 2 ) which holds those from opposite sides. 
         [0051]    The liquid crystal display panel  59  includes an active matrix substrate  51  and a counter substrate  52  between which liquid crystal (not shown) is filled. Although not shown, gate signal lines and source signal lines are arranged so as to cross each other, and at their intersections, switching devices (for example, thin-film transistors) are arranged which are needed to adjust the voltage applied to the liquid crystal. 
         [0052]    A polarizing film  53  is fitted on the light-entrance side of the active matrix substrate  51 , and another polarizing film  53  is fitted on the light-exit side of the counter substrate  52 . Structured as described above, the liquid crystal display panel  59  displays an image by exploiting variation of transmittance resulting from inclination of liquid crystal molecules. 
         [0053]    Next, a description will be given of the backlight unit  49 , which is located immediately under the liquid crystal display panel  59  and which supplies light (backlight) to the liquid crystal display panel  59 . The backlight unit  49  includes LED modules (light-emitting modules) MJ, a backlight chassis  10 , a reflective sheet  43 , a diffusive member  44 , a prism sheet  45 , and a prism sheet  46 . 
         [0054]    The LED modules MJ include mounting boards  21  and LEDs (light-emitting diodes)  22 . 
         [0055]    The mounting boards  21  are, for example, rectangular boards, and have a plurality of electrodes (not shown) arranged on their mounting surface  21 U. On top of these electrodes, LEDs  22  as light-emitting elements are fitted. The electrodes are arranged, on the mounting surface  21 U of each mounting board  21 , along two mutually crossing (for example, mutually perpendicular) directions (that is, the electrodes are in a lattice arrangement). 
         [0056]    In  FIG. 1 , four mounting boards  21  (hence LED modules MJ) are in a 2×2 lattice arrangement. This, however, is not meant as a limitation to that specific arrangement and that specific number of mounting boards  21 . On each mounting board  21 , LEDs  22  are mounted in a 4×4 lattice arrangement. This, however, is not meant as a limitation to that specific arrangement and that specific number of LEDs  22 . 
         [0057]    So long as the LEDs  22  are arranged close together so that the light from them mixes to produce planar light, there is no particular restriction on the number and arrangement of LEDs  22  and the number and arrangement of LED modules MJ. The mounting boards  21  may be hard boards made of a glass epoxy material or a paper phenolic material; or boards made of a composite epoxy material (CEN) composed of nonwoven glass fabric, glass cloth, and epoxy resin; or metal boards made of aluminum or iron. 
         [0058]    For convenience&#39; sake, in the group of LEDs  22  in a lattice arrangement, the direction of rows with a larger number of LEDs  22  is referred to as the X direction, and the direction of rows with a smaller number of LEDs  22  is referred to as the Y direction; the direction crossing (for example, perpendicular to) both the X and Y directions is referred to as the Z direction (the X direction corresponds to the longer sides of the screen of the liquid crystal display panel  59 , and the Y direction corresponds to the shorter sides of the screen of the liquid crystal display panel  59 ). 
         [0059]    The LEDs  22  are light sources (light-emitting devices, point light sources), and emit light by receiving electric current via the electrodes on the mounting boards  21 . Among the LEDs  22  in a lattice arrangement, the directions in which they emit light are aligned in one direction (the Z direction) so that the light from them mixes to produce planar light. Accordingly, the light-exit apertures  22 P of the LEDs  22  point in the Z direction (a light-exit aperture  22 P is the region of an LED  22  in which it emits light). 
         [0060]    As shown in  FIG. 1 , the backlight chassis (chassis)  10  is a box-shaped member, and accommodates, on its bottom surface  10 B, the LED modules MJ. The backlight chassis  10  will be described in detail later. 
         [0061]    The reflective sheet  43  is an optical sheet having a reflective surface  43 U, and covers the LED modules MJ in a lattice arrangement with the reverse surface to the reflective surface  43 U facing the LED modules MJ. The reflective sheet  43  has perforations  43 H at positions corresponding to the LEDs  22  on the LED modules MJ so that the LEDs  22  are exposed through the reflective surface  43 U. 
         [0062]    Such being the structure, even when part of the light emanating from the LEDs  22  travels toward the bottom surface  10 B of the backlight chassis  10 , it is reflected on the reflective surface  43 U of the reflective sheet  43 , and thus it then travels away from the bottom surface  10 B. The presence of the reflective sheet  43 , therefore, permits the light from the LEDs  24  to travel toward the diffusive member  44  opposite the reflective surface  43 U without loss. 
         [0063]    The diffusive member  44  is a plate-shaped optical member which is stacked on the reflective sheet  43  over the mounting surface  21 U on which the LEDs  22  are mounted. The diffusive member  44  receives and diffuses the light emanating from the LED modules MJ. That is, the diffusive member  44  diffuses the planar light formed by the LED modules MJ so that it illuminates the entire area of the liquid crystal display panel  59 . 
         [0064]    The prism sheets  45  and  46  are, for example, optical members that have prism shapes on their sheet plane to deflect light, and are located so as to cover the diffusive member  44 . The prism sheets  45  and  46  condense, and thereby increase the luminance of, the light emerging from the diffusive member  44 . The directions in which the light condensed by the prism sheets  45  and  46 , respectively, is made to diverge are in a mutually crossing relationship. 
         [0065]    In the backlight unit  49  (a direct backlight unit) structured as described above, the planar light formed by the LED modules MJ is passed through a plurality of optical members  44  to  46 , and is supplied to the liquid crystal display panel  59 . Receiving backlight BL from the backlight unit  49 , the non-luminous liquid crystal display panel  59  provides enhanced display performance. 
         [0066]    Now, the backlight chassis  10  will be described in detail with reference to, in addition to  FIGS. 1 and 2A  to  2 C, also  FIGS. 3 to 5 .  FIG. 3  is an exploded perspective view of four LED modules MJ and a backlight chassis  10  to which they are fitted.  FIG. 4  is a perspective view showing the LED modules MJ in the process of being fitted to the backlight chassis  10 .  FIG. 5  is a perspective view of the backlight chassis  10  having the LED modules MJ fitted to it (the package including the backlight chassis  10  and the mounting boards  21  is referred to as the electronic package PG). 
         [0067]    As shown in  FIG. 1 , forming an unclosed-loop-shaped cut in the bottom surface  10 B of the backlight chassis  10  produces a segment that can be raised from the bottom surface  10 B. The segment rises from the bottom surface  10 B of the backlight chassis  10  and then bends toward the bottom surface  10 B. Thus, the segment has the shape of a bent hook. Such a segment will be referred to as a hook  11 . The hook  11  is formed of the same material as the backlight chassis  10  (for example, flexible metal or resin). 
         [0068]    The hook (fastening portion)  11  thus includes a rising segment  11 P, which is the portion of the hook  11  that rises from the bottom surface  10 B of the backlight chassis  10 , and an overhanging segment  11 Q, which is the portion of the hook  11  that crosses the rising segment  11 P and that overhangs the mounting surface  21 U of a mounting board  21 . That is, as a whole, the hook  11  has a bent form like the letter L. 
         [0069]    The rising segment  11 P is the portion of the hook  11  between where it connects to the bottom surface  10 B of the backlight chassis  10  and where it bends midway (not necessarily precisely in the middle), and rises from the bottom surface  10 B in a direction approximately perpendicular to it. The length of the rising segment  11 P is about the same as the thickness of the mounting board  21 . 
         [0070]    The overhanging segment  11 Q is the portion of the hook  11  between where it bends midway and its tip, and overhangs the bottom surface  10 B of the backlight chassis  10 . Thus, between the overhanging segment  11 Q and the bottom surface  10 B of the backlight chassis  10 , there is a space in which a member can be held. In particular, when the length of the hook  11   p  supporting the overhanging segment  11 Q is about the same as the thickness of a mounting board  21 , between the overhanging segment  11 Q and the bottom surface  10 B of the backlight chassis  10 , there is a space in which the mounting board  21  can be fit. 
         [0071]    For example as shown in  FIG. 3 , four hooks  11  are arranged in a loop, one at each of the four sides of a mounting board  21 , which is rectangular. More specifically, each hook  11  is arranged to face a side of the mounting board  21 , with the tip of the overhanging segment  11 Q pointing to that side of the mounting board  21 , so that the side (edge) is held between the overhanging segment  11 Q and the bottom surface  10 B of the backlight chassis  10 . 
         [0072]    As shown in  FIG. 4 , a mounting board  21  is first held inclined relative to the bottom surface  10 B of the backlight chassis  10 , and one side of the mounting board  21  nearest to the bottom surface  10 B is put against a hook  11 . As the mounting board  21  is then inclined toward the bottom surface  10 B (as indicated by dotted-line arrows), the other sides of the mounting board  21  approach other hooks  11 . These hooks  11  warp against the approaching mounting board  21  and then straighten back, so that eventually, as shown in  FIG. 5 , all the sides of the mounting board  21  is held between the overhanging segments  11 Q of the hooks  11  and the bottom surface  10 B of the backlight chassis  10 . 
         [0073]    Thus, the mounting board  21  is held between the overhanging segments  11 Q of four hooks  11  and the bottom surface  10 B of the backlight chassis  10 , and is thereby prevented from moving upward (in the Z direction) off the bottom surface  10 B. In addition, the mounting board  21  is also held between the rising segments  11 P of opposite hooks  11 , and is thereby prevented from moving across the plane of the bottom surface  10 B of the backlight chassis  10  (i.e., across the XY plane defined by the X and Y directions). 
         [0074]    Providing, in this way, the backlight chassis  10  itself with a hook  11  for fastening a mounting board  21  eliminates the need for an extra holding member (such as screws and double-sided adhesive tape) for fastening the mounting board  21  to the backlight chassis  10 . This helps reduce the cost of the backlight unit  49 , hence the liquid crystal display device  69 . 
         [0075]    Moreover, the hook  11  is continuous with the backlight chassis  10 . Thus, even when the backlight unit  49  is subjected to impact or vibration, the hook  11  will not come off the backlight chassis  10  (the hook  11  is highly resistant to impact). 
         [0076]    In a case where the mounting board  21  is fastened to the backlight chassis  10  by use of a fastening member such as screws, the great trouble of turning the screws and the like is unavoidable. With hooks  11 , in contrast, simple fitting makes the trouble of fastening the mounting board  21  to the backlight chassis  10  comparatively small. This alleviates the trouble involved in the manufacture of the backlight unit  49 , hence the liquid crystal display device  69 . 
         [0077]    On the other hand, in a case where the mounting board  21  is fastened to the backlight chassis  10  by use of a fastening member such as double-sided adhesive tape, not only is the trouble of applying the double-sided adhesive tape unavoidable, but also the backlight unit  49  may become thicker by the thickness of the double-sided adhesive tape. With hooks  11 , in contrast, not only is the trouble of fastening the mounting board  21  to the backlight chassis  10  comparatively small, but also the backlight unit  49 , hence the liquid crystal display device  69 , does not become thicker. 
         [0078]    Moreover, on the occasion of repair and the like, a mounting board  21  that is fitted to the backlight chassis  10  with screws or double-sided adhesive tape is difficult to remove. With hooks  11 , in contrast, the mounting board  21  is easy not only to fit to but also to remove from the backlight chassis  10 . It is thus possible to realize a backlight unit  49  that is easy to rework. 
         [0079]    Although the above description deals with a case where one mounting board  21  is fastened to the bottom surface  10 B of the backlight chassis  10  by use of four hooks  11 , there is no particular restriction on the number of hooks  11 . Specifically, the number of hooks  11  may be three or less, or five or more. 
         [0080]    In a case where a hook  11 , at its rising segment  11 P, makes contact with the edge of a mounting board  21 , however, it is preferable that hooks  11  be arranged one at each of opposite sides of the mounting board  21  (that is, it is preferable that one hook  11  is provided at one side of the mounting board  21  and another hook  11  is provided at another side of the mounting board  21  opposite to the first-mentioned side). 
         [0081]    With this design, the mounting board  21  is prevented from moving across the plane of the bottom surface  10 B in the direction crossing the sides of the mounting board  21  at which it is held by the hooks  11  (that is, in the direction in which the hooks  11  are arranged) (that is, not only does each hook  11  hold the edge of the mounting board  21 , but a plurality of hooks  11  also holds the mounting board  11  itself, so that the mounting board  21  is more stably fastened to the backlight chassis  10 ). To prevent the mounting board  21  from moving in any direction across the plane, it is necessary that, for example as described above, all sides of the mounting board  21  be held by hooks  11 ). 
         [0082]    Instead, as shown in a sectional view in  FIG. 6  and a partial plan view in  FIG. 7 , a projection DG may be formed on the surface (inner surface  11 Qi), facing the mounting board  21 , of the overhanging segment  11 Q of the hook  11 , and a hole (or hollow)  21 H in which the projection DG fits may be formed on the mounting board  21 . With a single hook  11 , then, the mounting board  21  can be prevented from moving in any direction across the plane of the backlight chassis  10  (the mounting board  21  is prevented from rattling and shifting). 
         [0083]    In particular in a case where one mounting board  21  is fastened with one hook  11 , it is preferable that the hole  21 H be formed not circular but polygonal with three (triangular) or more vertices, and that the projection DG that fits in the hole  21 H be formed not hemispherical but in the shape of a block that fits the hole  21 H. With this design, the mounting board  21  is prevented from rotating about the projection DG. 
         [0084]    The number of hooks  11  including a DG is not limited to one for one mounting board  21 ; as shown in a plan view in  FIG. 8 , holes  21 H may be formed one for each side of the mounting board  21 , with hooks  11  arranged in correspondence to those holes  21 H. With this design, the mounting board  21  is more reliably prevented from moving with respect to the backlight chassis  10  (that is, the mounting board  21  is prevented from rattling and shifting, and the mounting board  21  is fastened to the backlight chassis  10  with increased strength). 
         [0085]    Instead, whereas a projection DG is formed on the hook  11 , no hole  21 H for the projection DG to fit in may be formed. Usually, forming the projection DG on the inner surface  11 Qi of the overhanging segment  11 Q facing the mounting surface  21 U of the mounting board  21  makes the distance between the tip of the projection DG and the bottom surface  10 B of the backlight chassis  10  shorter than the distance between the inner surface  11 Qi of the overhanging segment  11 Q and the bottom surface  10 B (that is, the distance between the overhanging segment  11 Q and the bottom surface  10 B of the backlight chassis  10  is made shorter by the height of the projection DG). 
         [0086]    Then, when the hook  11 , between it and the bottom surface  10 B of the backlight chassis  10 , holds the mounting board  21 , the projection DG increases the pressing force against the mounting surface  21 U. Thus, even with no hole  21 H in the mounting board  21 , the hook  11  can satisfactorily prevent the mounting board  21  from moving. The cost of forming the hole  21 H in the mounting board  21  is also cut. 
         [0087]    As the LEDs  22  emit light, they generate heat, and the heat collects in the LEDs  22  and also in the mounting board  21  on which the LEDs  22  are mounted. The heat causes not only lowering of the light emission efficiency of the LEDs  22  but also deterioration (secular deterioration) of the mounting board  21 . 
         [0088]    In a case where the backlight chassis  10  is made of, for example, metal, it is preferable that the hook  11  shown in  FIG. 3  be formed by cutting and raising part of the bottom surface  10 B of the backlight chassis  10 . With this design, forming the hook  11  in the backlight chassis  10  leaves there an opening (ventilation opening)  12  that leads to the outside. 
         [0089]    Thus, when the LED modules MJ are placed over the bottom surface  10 B of the backlight chassis  10  and are fastened to backlight chassis  10  with hooks  11 , the inside of the backlight unit  49  is not hermetically closed, and thus outside air enters through ventilation openings  12 . Thus, even when the LEDs  22  generate heat, the heat not only dissipates by conducting to the backlight chassis  10  with which the mounting board  21  makes contact, but is also lowered by outside air entering through the ventilation openings  12 . The heated air is then discharged outside (the heat is rejected). 
         [0090]    That is, the heat collecting in the LEDs  22  and in the mounting boards  21  dissipate by conducting not only to the backlight chassis  10  but also to outside air (that is, heat dissipates also by convection). This prevents deterioration of the LEDs  22  and the mounting boards  21 , and prevents lowering of the light emission efficiency of the LEDs  22  (that is, it prevents lowering of the luminance of the planar light from the backlight unit  49 , and thereby permits light with desired luminance to be produced with comparatively low power consumption). In addition, since the hooks  11  are formed by cutting and raising part of the bottom surface  10 B of the backlight chassis  10 , there is no need for an extra member for forming the hooks  11 . 
         [0091]    For further dissipation of the heat collecting in the LED modules MJ, a window  13  may be formed in the bottom surface  10 B of the backlight chassis  10  to make it shaped like a skeleton. For example, as shown in a perspective view in  FIG. 9  and a plan view in  FIG. 10 , it is preferable that, on the rear side of a mounting board  21  fastened to the bottom surface  10 B of the backlight chassis  10  (on the side of the reverse surface  21 B to the mounting surface  21 U on which LEDs  22  are mounted), a window  13  be formed which is geometrically similar to the contour of the mounting board  21 . 
         [0092]    With this design, owing to the window  13  which has a similar function to and larger than the ventilation opening  12 , the heat collecting in the LED modules MJ dissipates to outside air more efficiently. 
         [0093]    The shape of the window  13  is not limited to one geometrically similar (for example, rectangular) to that of the mounting board  21 . For example, the window  13  may be rhombic as shown in  FIG. 11 , or circular as shown in  FIG. 12 . Although in  FIGS. 10 to 12 , windows  13  of the same type are formed in the bottom surface  10 B of one backlight chassis  10 , this is not meant as a limitation; as shown in  FIG. 13 , triangular windows  13  and trapezoid windows  13  may be formed in a mixed fashion in the bottom surface  10 B. 
         [0094]    As shown in  FIGS. 10 to 13 , it is preferable that, of the bottom surface  10 B of the backlight chassis  10  shaped like a skeleton, the frame-like portion (indicated by dash-dot-dot lines) other than the windows  13  be left so as to have a crossing shape. With the frame-like portion of the bottom surface  10 B left to have a crossing shape, even through the backlight chassis  10  is lighter by the weight removed for the windows  13 , the backlight chassis  10  remains satisfactorily strong. 
         [0095]    An example of the material of the backlight chassis  10  described above is metal, and there is no particular restriction on the kind of metal. For example, when the material of the backlight chassis  10  is metal, iron may be used as one example; instead, as a metal lighter and having higher heat dissipation than iron, aluminum or an aluminum alloy (for example, any of Al—C, Al—Mn, Al—Si, Al—Mg, Al—Mg—Si, and Al—Mg—Zn alloys) may be used. 
         [0096]    Forming the backlight chassis  10  out of a material with comparatively high thermal conductivity as mentioned above permits the heat collecting in the LEDs  22  and the mounting boards  21  to dissipate by conducting to the backlight chassis  10  efficiently. This prevents deterioration of the LEDs  22  and the mounting board  21 , and hence prevents lowering of the light emission efficiency of the LEDs  22 . Moreover, using an aluminum alloy, which has a specific gravity about one-third of that of iron, makes the backlight unit  49 , hence the liquid crystal display device  69 , lighter. 
         [0097]    The material of the backlight chassis  10  may be resin. For example, the backlight chassis  10  may be formed of resin integrally with hooks  11 . One example of such resin is carbon fiber-reinforced plastic (CFRP). CFRP has a specific gravity of about 1.4 g/cm 3 , which is about half that of an aluminum alloy, namely about 2.7 g/cm 3 , and in addition has higher thermal conductivity than an aluminum alloy. 
         [0098]    Thus, a backlight chassis  10  made of CFRP, compared with one made of aluminum alloy, prevents lowering of the light emission efficiency of the LEDs  2  more effectively and is lighter. 
         [0099]    Other means, than proper selection of the material of the backlight chassis  10 , of efficiently dissipating the heat collecting in the LED modules MJ include the following. 
         [0100]    One means is to form a coarse surface on at least part of the backlight chassis  10  as shown in a three-view diagram in  FIG. 14  (composed of a plan view of the rear side of the bottom surface  10 B of the backlight chassis  10  and two side views of the side surface of the backlight chassis  10  as seen from two directions). 
         [0101]    Forming a coarse surface on the side surface  10 S and bottom surface  10 B of the backlight chassis  10  in this way increases the surface area over which it makes contact with outside air, and thus the heat of the LED modules MJ that has conducted to the backlight chassis  10  dissipates efficiently. 
         [0102]    In particular, forming a coarse surface on an outer surface of the backlight chassis  10 , that is, on the outer (outward facing) side of the side surface  10 S and on the outer (outward facing) side of the bottom surface  10 B, permits the backlight chassis  10  with that coarse surface to make contact with outside air (that is, fresh outside air) outside the backlight unit  49 , and this ensures dissipation of heat. 
         [0103]    The surface coarsing is not restricted by the material of the backlight chassis  10 . That is, surface coarsing may be applied irrespective of whether the backlight chassis  10  is made of metal, such as iron, aluminum, or aluminum alloy, or resin, such as CFRP. 
         [0104]    Another means of efficiently dissipating the heat collecting in the LED modules MJ is to apply high-emissivity paint to the backlight chassis  10 . High-emissivity paint is paint that exhibits increased heat emission by its containing a non-metal substance, such as carbon (with an emissivity of about 0.8), graphite (with an emissivity of about 0.93), or the like, or a metal compound, such as nickel oxide (NiO, with an emissivity of about 0.9), silicon dioxide (SiO 2 , with an emissivity of bout 0.83), tantalum carbide (TaC, with an emissivity of about 0.81), or the like. 
         [0105]    Applying such high-emissivity paint to, for example, the side surface  10 S and bottom surface  10 B of the backlight chassis  10  increases the emission (radiation) of far-infrared rays from those surfaces. Thus, a backlight chassis  10  having high-emission paint applied to at least part of it ensures dissipation of heat. 
         [0106]    In particular, applying high-emission paint to the backlight chassis  10  on the outer (outward facing) side of the side surface  10 S, around four sides, and on the outside side (rear side) of the bottom surface  10 B permits the backlight chassis  10  with that painted part to emit heat into outside air outside the backlight unit  49 , and this ensures dissipation of heat. 
         [0107]    The high-emissivity paint is not restricted by the material of the backlight chassis  10  to which it is applied. That is, high-emissivity paint may be applied irrespective of whether the backlight chassis  10  is made of metal, such as iron, aluminum, or aluminum alloy, or resin, such as CFRP. High-emissivity paint may be applied to a coarse surface provided on, for example, the outer surface of the backlight chassis  10 . 
         [0108]    High-emissivity paint may be applied to the reverse surface  21 B of the mounting board  21  of the LED modules MJ. Also with this design, the heat collecting in the LED modules MJ dissipates efficiently. There is no particular restriction on how the high-emission paint is applied; it may be applied, for example, by spraying or with a brush. 
       Other Embodiments 
       [0109]    The present invention may be carried out in any manners other than specifically described by way of embodiments above, and allows many modifications and variations. 
         [0110]    For example, there is no particular restriction on how the backlight chassis  10 , including hooks  11  and windows  13 , is formed, For example, in a case where the backlight chassis  10  is made of metal, it may be formed by subjecting flat sheet metal with a thickness of about 0.5 to about 2 mm to pressing, punching, bending, or other processing. In a case where the backlight chassis  10  is made of resin, it may be formed by molding. 
         [0111]    There is no particular restriction on how a coarse surface is formed on the backlight chassis  10 . For example, to form a coarse surface with fine irregularities on different surfaces of the backlight chassis  10 , etching is performed by use of a mask pattern film having a coarse surface pattern with fine irregularities. To form a coarse surface with fine irregularities on different surfaces of the backlight chassis  10  at low cost, embossing is performed which involves swage-shaping using a die having a coarse surface pattern. 
         [0112]    In the backlight unit  49  which outputs the light from the LEDs  22  mounted on the mounting surface  21 U of the mounting boards  21 , as shown in  FIG. 1 , the reflective sheet  43  covers the mounting surface  21 U with the reflective surface  43 U facing the outside and the reverse surface to the reflective surface  43 U facing the mounting surface  21 U. 
         [0113]    As shown in  FIG. 15A to 15C , in the reflective sheet  43 , there may be formed perforations  43 H through which only the light exit apertures  22 P (light-exit region) of the LEDs  22  are exposed to the outside.  FIG. 15A  is a plan view of the backlight chassis  10  having, stacked on its bottom surface  10 B, the LED modules MJ and the reflective sheet  43 ;  FIG. 15B  is a sectional view of the backlight chassis  10  etc. shown in  FIG. 15A  along line A 2 -A 2 ′ as seen from the direction of arrows; and  FIG. 15C  is a sectional view of the backlight chassis  10  etc. shown in  FIG. 15A  along line B 2 -B 2 ′ as seen from the direction of arrows. 
         [0114]    When a comparison is made between the area of a reflective sheet  43  that exposes only the light-exit apertures  22 P of the LEDs  22  through the perforations  43 H and the area of a reflective sheet  43  that exposes the entire LEDs  22  through the perforations  43 H, the reflective sheet  43  that exposes only the light-exit apertures  22 P of the LEDs  22  has a larger reflective surface  43 U. 
         [0115]    Accordingly, the front luminance plotted against the position on a sectional view of the backlight unit  49  describes curves as shown in  FIG. 16 . Specifically, the solid-line curve represents the front luminance attributable to the light emitted from the LEDs  22  and the light reflected from a reflective sheet  43  that exposes only the light-exit apertures  22 P of the LEDs  22  through the perforations  43 H, and the dotted-line curve represents the front luminance attributable to the light emitted from the LEDs  22  and the light reflected from a reflective sheet  43  that exposes the entire LEDs  22  through the perforations  43 H (a sectional view of the backlight unit  49  corresponding to the solid-line curve is shown under the graphs, and a sectional view of the backlight unit  49  corresponding to the dotted-line curve is shown over the graphs). 
         [0116]    The two graphs reveal that the solid-line curve indicates less difference than the dotted-line curve. That is, the planar light formed by the light emitted from the LEDs  22  and the light reflected from a reflective sheet  43  that exposes only the light-exit apertures  22 P of the LEDs  22  through the perforations  43 H is less likely to have uneven light distribution. This results from the portions of the LEDs  22  around the light-exit apertures  22 P, which do not reflect light, being covered by the reflective sheet  43 , leading to increased reflectance. 
         [0117]    That is, the part of the reflective surface  43 U of the reflective sheet  43  where it does not reflect light (absorbing portion, the portion between the rim of the perforations  43 H and the light-exit apertures  22 P) is eliminated, with a result that, whereas a reflective sheet  43  with an absorbing portion has a reflectance of about 50% to 80%, a reflective sheet  43  with narrowed perforations  43 H and hence a smaller absorbing portion has a reflectance of 95% or more. 
         [0118]    With this design, it is possible to increase the luminance of the planar light without increasing the electric current supplied to the LEDs  22 . As a result, the backlight unit  49  can provide high-quality planar light with less uneven light distribution with comparatively low power consumption (that is, light with desired luminance can be produced with comparatively low power consumption). 
         [0119]    Making the height of the LEDs  22  (that is, the height from the mounting surface  21 U to the light-exit apertures  22 P) and the thickness of the overhanging segments  11 Q of the hooks  11  approximately equal as shown in  FIG. 15B  makes it more likely that the reflective sheet  43 , when laid over the mounting surface  21 U having the LEDs  22  mounted on it, lies flat without wrinkles. 
         [0120]    Laying the reflective sheet  43  flat in that way makes it easier for the light reflected from it to travel toward the diffusive member  43 , and makes loss of light less likely. Thus, the light output from the backlight unit  49  has still less uneven light distribution. 
       LIST OF REFERENCE SIGNS 
       [0000]    
       
         
           
               10  backlight chassis (chassis) 
               11  hook (fastening portion) 
               11 P rising segment 
               11 Q overhanging segment 
             DG projection 
               11 B bottom surface of backlight chassis 
               11 S side surface of backlight chassis 
               12  ventilation opening 
               13  opening 
               21  mounting board 
               21 U mounting surface 
               21   b  reverse surface to mounting surface 
               21 H hole 
               22  LED 
               22 P light-exit aperture (light-exit region) 
             MJ LED module 
               43  reflective sheet 
               43 H perforation 
               44  diffusive member 
               45  prism sheet 
               46  prism sheet 
               49  backlight unit (lighting device) 
               59  liquid crystal display panel (display panel) 
               69  liquid crystal display device (display device)