Abstract:
A backlight chassis is constituted by combining a right end chassis plate, a left end chassis plate, and an intermediate chassis plate obtained by cutting a metal sheet into a predetermined shape and pressing. A trough portion is formed in each chassis plate at a portion to be the long side of the backlight chassis, and the trough portions are superimposed at the boundary of adjoining chassis plates. Furthermore, a superimposed portion constituting a beam-shaped portion is provided at the boundary of adjoining chassis plates. The chassis plates are coupled by screws penetrating the superimposed portion of the trough portions or the beam-shaped portions. The right end chassis plate and the left end chassis plate have point symmetric shapes.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a backlight chassis for a liquid crystal display panel. 
     2. Description of the Related Art 
     A backlight chassis holding a light source lamp as a backlight for a liquid crystal display panel is, in a case in which the liquid crystal display panel is a large one, typically formed of a metal sheet (specifically, a steel sheet) in view of strength and cost. An example of such a backlight chassis made of a metal sheet is disclosed in JP-A-2005-107499. 
     Although the backlight chassis disclosed in JP-A-2005-107499 has a ladder configuration, backlight chassis are also often formed to have a tray configuration. A backlight chassis having a tray configuration has an increased size and suffer the following disadvantages. 
     That is, so called “oil canning”, in which the center of a metal sheet is popped back or forth so as to be warped, occurs. In some cases, the center of a metal sheet is even warped to be as much as several millimeters deviated from the planned geometric plane. The thus-structured backlight chassis generates abnormal noise (chattering noise) when it receives vibration. In addition, a light source lamp (e.g., a cold-cathode tube) incorporated in such a backlight chassis is of a long length, and thus, when vibration (for example, acoustic vibration of a television speaker) is transferred thereto, the light source lamp makes noise. To avoid such noise, the center portion of the light source lamp is fixed to the backlight chassis with a clip. However, if a large impact is received due to the occurrence of oil canning, the engagement between the light source lamp and the clip may be released. If the engagement is not released, the light source lamp itself will be warped, and as a result, a crack may occur in the lamp, or the distance between the lamp and the liquid crystal display panel may become non-uniform to cause non-uniform brightness. To cope with these problems, a large number of backlight chassis are provided with a reinforcement metal fitting on the rear surface thereof to reduce oil canning. 
     SUMMARY OF THE INVENTION 
     In view of the above problems, preferred embodiments of the present invention provide a backlight chassis for a liquid crystal display panel that stays resistant to oil canning in a metal sheet even when it is produced to have a large area. 
     According to a preferred embodiment of the present invention, a backlight chassis for a liquid crystal display panel is provided with a plurality of chassis plates each formed of a metal sheet that is cut and stamped into a predetermined shape. Here, each of the chassis plates corresponds to one of sections into which a whole chassis is divided, and adjoining chassis plates are connected to each other to form a whole chassis. 
     With this structure, oil canning in the metal sheet is dispersed to each of the chassis plates as minor oil canning. As a result, even with a structure in which a lamp is held at its middle portion by a clip fitted to a backlight chassis, the engagement between the clip and the lamp is prevented from being released, abnormal noise is reduced, and brightness is less likely to become non-uniform. 
     According to a preferred embodiment of the present invention, in the above-structured backlight chassis for a liquid crystal display panel, it is preferable that each of the chassis plates have a trough-shaped portion or a beam-shaped portion in a border portion with an adjoining chassis plate, and that the trough-shaped portions or the beam-shaped portions of adjoining chassis plates be superposed one on top of the other to connect the adjoining chassis plates to each other. 
     With this structure, the trough-shaped portion or the beam-shaped portion functions as a reinforcing metal fitting to increase the rigidity of the backlight chassis, and this helps reduce oil canning. 
     According to a preferred embodiment of the present invention, in the above-structured backlight chassis for a liquid crystal display panel, it is preferable that adjoining chassis plates be connected to each other with a screw that is screwed into a superposition portion of the trough-shaped portions or a superposition portion of the beam-shaped portions. 
     With this structure, large-area backlight chassis can be assembled even in a factory having no large-scale welding machine available. 
     According to a preferred embodiment of the present invention, in the above-structured backlight chassis for a liquid crystal display panel, it is preferable that each of the chassis plates have a beam-shaped portion in a border portion with an adjoining chassis plate, and that beam-shaped portions of adjoining chassis plates be superposed one on top of the other, and a trough-shaped member, which is another component, be superposed on edges of the plurality of chassis plates perpendicular or substantially perpendicular to the beam-shaped portions to connect adjoining chassis plates to each other. 
     With this structure, the beam-shaped portions and the trough-shaped member function as enhancing metal fittings to increase the rigidity of the backlight chassis, and this helps reduce oil canning. 
     According to a preferred embodiment of the present invention, in the above-structured backlight chassis for a liquid crystal display panel, it is preferable that adjoining chassis plates be connected to each other with a screw that is screwed into a superposition portion of the beam-shaped portions, and a screw that is screwed into a superposition portion of the trough-shaped member and the edges of the chassis plates. 
     With this structure, large-area backlight chassis can be assembled even in a factory having no large-scale welding machine available. 
     According to a preferred embodiment of the present invention, in the above-structured backlight chassis for a liquid crystal display panel, it is preferable that division of the whole chassis be performed along a division line that is parallel or substantially parallel to a short side of the whole chassis. 
     With this structure, it is possible to obtain a chassis plate that is shaped and sized so as to be handy. 
     According to a preferred embodiment of the present invention, in the above-structured backlight chassis for a liquid crystal display panel, it is preferable that a left-end chassis plate and a right-end chassis plate be partitioned by the division line, and that the left-end chassis plate and the right-end chassis plate be point-symmetrical with each other. 
     With this structure, the left-end and right-end chassis plates can be produced as identical members, and this helps reduce production cost. 
     According to a preferred embodiment of the present invention, it is possible to provide a backlight chassis for a liquid crystal display panel that is made of a metal sheet and that suffers only minor oil canning despite having a large area, and in which abnormal noise and brightness non-uniformity is prevented from occurring. 
     Other features, elements, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the present invention with reference to the attached drawings 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded perspective view of a liquid crystal display device according to a first preferred embodiment of the present invention. 
         FIG. 2  is a plan view of a backlight chassis. 
         FIG. 3  is an enlarged partial plan view of a backlight chassis in a disassembled state. 
         FIG. 4  is an enlarged partial plan view of a backlight chassis in an assembled state. 
         FIG. 5  is an enlarged partial perspective view corresponding to  FIG. 3 . 
         FIG. 6  is an enlarged partial sectional view of a backlight chassis. 
         FIG. 7  is an enlarged partial sectional view showing a modified example of the portion shown in  FIG. 6 . 
         FIG. 8  is a plan view of a backlight chassis to which a light source lamp is attached. 
         FIG. 9  is a sectional view of the backlight chassis shown in  FIG. 8 . 
         FIG. 10  is an enlarged front view of a clip holding a middle portion of a light source lamp. 
         FIG. 11  is a plan view of a backlight chassis of a second preferred embodiment. 
         FIG. 12  is a sectional view taken along line A-A Line of  FIG. 11 . 
         FIG. 13  is an enlarged partial sectional view of the backlight chassis according to the second preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A description will be given below of a first preferred embodiment of the present invention with reference to  FIGS. 1 to 10 . In the exploded perspective view of  FIG. 1 , components of a liquid crystal display device are illustrated under an assumption that the liquid crystal display is to be assembled such that its display surface faces upward. Located at the lowermost position is a backlight chassis on which the present preferred embodiment of the present invention is focused, and the structure of the backlight chassis will be described later in detail. On the backlight chassis, a reflection sheet  2  is laid, and over the reflection sheet  2 , a plurality of light source lamps  3  are arranged. A straight cold-cathode tube is typically used as the light source for a backlight, but a lamp of different type, such as a hot-cathode tube or a xenon lamp, can be used. 
     An optical-sheet assembly  4 , which includes a diffusion plate, a lens sheet, a deflection/reflection sheet, and a diffusion sheet, is placed over the lamps  3 . The optical-sheet assembly  4  is used to adjust properties of light emitted from the light source lamps  3 . 
     The optical-sheet assembly  4  is fitted to a backlight chassis  1  with a picture-frame shaped frame  5 . A liquid crystal display panel  6  is placed on the frame  5 . Placed at the uppermost stage is a picture-frame shaped bezel  7 . The bezel  7  fixes the liquid crystal display panel  6  to the backlight chassis  1 , and also refines the overall appearance of the liquid crystal display device. 
     Next, the structure of the backlight chassis  1  will be described. The backlight chassis  1  is preferably rectangular or substantially rectangular in plan view, and has a shape of a tray having rising peripheral edges. The backlight chassis  1  is formed preferably by combining a plurality of chassis plates each formed of a metal sheet (in this preferred embodiment, a steel sheet) cut and stamped into a predetermined shape. Each of the chassis plates is one of sections into which a whole chassis is divided. In this preferred embodiment, the backlight chassis  1  is preferably partitioned into three chassis plates by two division lines that are parallel or substantially parallel to the short side of the rectangular or substantially rectangular plan shape of the backlight chassis  1 . The three chassis plates preferably include a left-end chassis plate  10 L, a right-end chassis plate  10 R, and a middle chassis plate  10 M located between the left-end and right-end chassis plates  10 L and  10 R. 
     The left-end and right-end chassis plates  10 L and  10 R are stamped as components having the same shape by using a same die, and then, with the orientation of one of them reversed, they are arranged to be point-symmetrical with each other. Clip fitting portions are arranged on the left-end and right-end chassis plates  10 L and  10 R to hold middle portions of the light source lamps  3 , and the clip fitting portions are arranged out of the point symmetry between the left-end and right-end chassis plates  10 L and  10 R. This will be described later in detail. 
     The left-end and right-end chassis plates  10 L and  10 R naturally have a same area, and the middle chassis plate  10 M also has substantially the same area as the left-end and right-end chassis plates  10 L and  10 R. In other words, the left-end, right-end, and middle chassis plates  10 L,  10 R, and  10 M are obtained by dividing the backlight chassis  1  into three substantially equal portions. 
     Trough-shaped portions are formed in the left-end, right-end, and middle chassis plates  10 L,  10 R, and  10 M at portions thereof that form longer sides of a whole chassis. Specifically, in the left-end chassis plate  10 L, trough-shaped portions  11 L are formed at top and bottom edges thereof in  FIG. 2 . Likewise, trough-shaped portions  11 R are formed at top and bottom edges of the right-end chassis plate  10 R in  FIG. 2 , and trough-shaped portion  11 M are formed at top and bottom edges of the middle chassis plate  10 M in  FIG. 2 . The trough-shaped portions  11 L,  11 R, and  11 M preferably have a same sectional shape, that is, a U-shape that is open downward, for example. The trough-shaped portions  11 L,  11 R, and  11 M are connected together such that adjoining trough-shaped portions are connected to each other at border portions between the left-end and middle chassis plates  10 L and  10 M and between the middle and right-end chassis plates  10 M and  10 R. Thus, contiguous trough shapes are formed. 
     Beam-shaped portions extending in the short-side direction of the whole chassis are formed in each of the left-end chassis plate  10 L, the right-end chassis plate  10 R, and the middle chassis plate  10 M. The “beam-shaped portion” is a ridge-shaped or furrow-shaped structure that rises up from a flat surface portion of a chassis plate and increases the material mechanical modulus of section. The beam-shaped portions of the left-end and right-end chassis plates  10 L and  10 R are preferably formed in a different way from the beam-shaped portion of the middle chassis plate  10 M. What is common to the chassis plates is that each of the chassis plates  10 L,  10 R, and  10 M has a beam-shaped portion at least at a border portion with an adjoining chassis plate. 
     In each of the left-end and right-end chassis plates  10 L and  10 R, a rising portion  12  is provided at an edge thereof located farther from a center of the backlight chassis  1 . The rising portion  12  is one of beam-shaped portions provided in plurality in each of the left-end chassis plate  10 L and the right-end chassis plate  10 R. The rising portions  12 , together with the trough-shaped portions  11 L,  11 R, and  11 M, give the backlight chassis  1  a tray configuration. 
     Edges of the left-end chassis plate  10 L and the right-end chassis plate  10 R that are located closer to the center of the backlight chassis  1  are border portions with the middle chassis plate  10 M flanked by them. At these portions, both of the left-end chassis plate  10 L and the right-end chassis plate  10 R have a superposition portion  13  to be superposed on the middle chassis plate  10 M. As shown in  FIG. 6 , the superposition portions  13  are each L-shaped in section, and this L-shaped section makes the superposition portions  13  function as beam-shaped portions of the left-end chassis plate  10 L and the right-end chassis plate  10 R. Incidentally, the superposition portion  13  of the left-end chassis plate  10 L and that of the right-end chassis plate  10 R face opposite directions (see  FIG. 9 ). 
     As for the middle chassis plate  10 M, its left edge is a border portion with the left-end chassis plate  10 L and its right edge is a border portion with the right-end chassis plate  10 R. At these border portions, superposition portions  14  are formed. The superposition portions  14  are also L-shaped in section. The superposition portions  14  at the right and left edges of the middle chassis plate  10 M are oriented in opposite directions, but, in section, a lateral stroke of letter L of the superposition portions  14  is laid under a lateral stroke of letter L of the superposition portions  13 . The L-shaped sectional shape causes the superposition portions  14  to function as beam-shaped portions of the middle chassis plate  10 M. 
     In this way, the trough-shaped portions and the beam-shaped portions are arranged along the four sides of each of the left-end chassis plate  10 L, the right-end chassis plate  10 R, and the middle chassis plate  10 M. This increases the rigidity of the backlight chassis  1  both in the long-side and short-side directions, and thus reduces oil canning occurring in center portions of the chassis plates (indicated with C in  FIG. 2 ). 
     Superposition portions are also formed in border portions between the trough-shaped portions  11 L and  11 M and between the trough-shaped portions  11 R and  11 M. A description will be given of the structure of these superposition portions, taking the superposition portion between the trough-shaped portions  11 L and  11 M as an example. 
     As shown in  FIGS. 3 to 5 , a cutout portion  15  is formed in the trough-shaped portion  11 L on a side facing the center of the left-end chassis plate  10 L. A cutout portion  16  is formed in the trough-shaped portion  11 M on a side facing outside of the middle chassis plate  10 M. Remaining portions of the trough-shaped portions  11 L and  11 M fit into the cutout portions  16  and  15 , respectively, such that the trough-shaped portions  11 L and  11 M interlace with each other. 
     A connection piece  17  is provided in a vertical wall of the trough-shaped portion  11 L facing outside of the left-end chassis plate  10 L. The connection piece  17  is depressed toward an inside of the trough-shaped portion  11 L by a distance equivalent to the thickness of the metal sheet of which the trough-shaped portion  11 L is made. In the trough-shaped portion  11 M, at a position corresponding to the position of the connection piece  17 , a connection piece  18  is formed. The connection piece  18  is not depressed toward inside the trough-shaped portion  11 M. When the trough-shaped portions  11 L and  11 M are brought close to each other, the cutout portions  15  and  16  engage with each other, and at the same time, the connection piece  18  is superposed on the connection piece  17  from outside, and thus the state shown in  FIG. 4  is achieved. Pilot holes  19  and  20  (see  FIG. 5 ) formed in the connection pieces  17  and  18  for screws are aligned with each other. Into the pilot holes  19  and  20  aligned with each other, a screw  21  (see  FIG. 4 ), which is a self-tapping screw, is screwed to penetrate therethrough, and thereby the trough-portions  11 L and  11 M are connected to each other. To be precise, it is in the pilot hole  19  that screw grooves are formed by tapping, and the pilot hole  20  has an inner diameter large enough to allow easy passage of the screw  21  therethrough. 
     The superposition portion between the trough-shaped portions  11 R and  11 M is structured and fixed in the same manner as described above, except that the structure is laterally opposite to the above-described structure. 
     When the trough-shaped portions  11 R and  11 M are superposed and the trough-shaped portions  11 R and  11 M are superposed, the superposition portions  13  and  14  are also superposed. In the same manner as in the trough-shaped portions, the superposition portions  13  and  14 , after being superposed one on top of the other, are also connected to each other with a screw  21  penetrating therethrough. 
     When the left-end and middle chassis plates  10 L and  10 M are connected to each other and the right-end and middle chassis plates  10 R and  10 M are connected to each other as described above, the trough-shaped portions  11 L,  11 R, and  11 M are connected to form a line of trough-shaped portion whereby the rigidity of the backlight chassis  1  in the long-side direction is increased to reduce oil canning. In addition, since the left-end, right-end, and middle chassis plates  10 L,  10 R, and  10 M are provided with beam-shaped portions extending in the short-side direction of the backlight chassis  1 , the rigidity of the backlight chassis  1  in the short-side direction is increased to reduce oil canning. 
     A modified example of the structure of the superposition portion is shown in  FIG. 7 . Here, the superposition portion  13  preferably has a form of U-shaped groove in section, while the superposition portion  14  is C-shaped in section, for example. These sectional shapes cause the superposition portions  13  and  14  to function as beam-shaped portions of the left-end, right-end, and middle chassis plates  10 L,  10 R, and  10 M. The superposition portions  13  and  14  can be firmly connected to each other by setting the superposition portion  14  in the superposition portion  13  and fastening them together with screws  21  penetrating through them in two directions of vertical and horizontal directions. 
     In both examples shown in  FIGS. 6 and 7 , the superposition portions  13  and  14  together define a groove-shaped space, and since the screws  21  are screwed into them toward the groove-shaped space, it is possible to avoid tip-ends of the screws  21  interfering with some member and to avoid some member being caught on the tip-ends of the screws  21 . 
     According to the example shown in  FIG. 6 , the groove formed with superposition portions  13  and  14  is significantly wide, but, being completely covered with the reflection sheet  2 , it does not have any negative effect on the optical properties of the backlight chassis  1 . 
     The superposition portions  13  and  14  may have various shapes other than those shown in  FIGS. 6 and 7 . Likewise, the superposition portions in the trough-shaped portions may have various shapes in addition to the shapes shown in  FIGS. 3 to 5 . 
     In the left-end and right-end chassis plates  10 L and  10 R is formed a fitting portion  23  for a socket  22  (see  FIGS. 8 and 9 ) that holds an end of the light source lamp  3 . The fitting portion  23  is a through hole of a predetermined shape into which two sockets  22  are fitted. The fitting portion  23  is formed in plurality such that a plurality of fitting portions  22  are aligned in the short-side direction along an edge of each of the left-end and right-end chassis plates  10 L and  10 R that is farther from the center of the backlight chassis  1 . Incidentally, the sockets  22  are electrically connected to an unillustrated control substrate in a control box  24  (see  FIG. 9 ) provided on a bottom surface of the backlight chassis  1 . 
     The light source lamp  3  is of a long length, and makes noise when vibration is transferred thereto. To avoid this, the middle portion of the light source lamp  3  is fixed to the backlight chassis  1  with a clip  25 . 
     The structure of the clip  25  is shown in  FIG. 10 . The clip  25  is structured such that a lamp holder  25   b  having a C-shape that is open upward is provided on a top surface of a flat base  25   a  that is rectangular or substantially rectangular in plan view. The lamp holder  25   b  holds the light source lamp  3  with its elasticity, and a total of two lamp holders  25   b  are provided one at each end in a longitudinal direction of the base  25   a . On a bottom surface of the base  25   a , two snap pins  25   c  each having a bulging head portion and a slot groove are formed at an interval in the longitudinal direction of the base  25   a . The clip  25  preferably is integrally formed of an elastic synthetic resin. 
     A fitting portion  26  for the clip  25  is provided on the backlight chassis  1  and the reflection sheet  2  that is adhered to a top surface of the backlight chassis  1 . The fitting potion  26  includes two through holes through each of which a snap pin  25   c  passed. When the snap pin  25   c  is pressed against the fitting portion  26  from above, the bulging head portion of the snap pin  25   c  shrinks to pass through the hole. Coming out of the bottom surface of the backlight chassis  1 , the head portion of the snap pin  25   c  springs back to its original bulging state, and thus the clip  25  is brought into a fitted state. 
     The light source lamp  3  is held at two positions in the middle portion thereof using two clips  25 . One clip  25  holds two light source lamps  3 , and thus two fitting portions  26  are provided at an interval in the length direction of the light source lamp  3  for every two light source lamps  3 . 
     By holding the light source lamps  3  at middle portions thereof with the clips  25 , the light source lamps  3  can be prevented from being vibrated to make noise. The clips  25  are fitted on the left-end chassis plate  10 L, the right-end chassis plate  10 R, or the middle chassis plate  10 M. The left-end, right-end, and middle chassis plates  10 L,  10 R, and  10 M all suffer only a small degree of oil canning, and thus, even when an impact is applied to the backlight chassis  1 , no source lamp  3  comes off the clips  25 . 
     The clips  25  are preferably formed of a synthetic resin that is poor in thermal conductivity, yet they conduct to the backlight chassis  1  a certain ratio of heat generated by the light source lamps  3 . By being thus deprived of heat, the light source lamps  3  deteriorate in brightness around the clips  25 . If the clips  25  are arranged in a line in the short-side direction of the backlight chassis  1 , a zone having markedly low brightness appears. To prevent this from happening, the clips  25  are dispersedly arranged. A specific method of such an arrangement will be described with reference to  FIGS. 2 and 8 . 
     In  FIGS. 2 and 8 , the fitting portions  26  for the top two light source lamps  3  in the figures are set to be positioned as follows. That is, one is positioned close to the left edge of the middle chassis plate  10 M, and the other is positioned close to the left edge of the right-end chassis plate  10 R. The fitting portions  26  for the next two light source lamps  3  located right under the top two light source lamps  3  are positioned as follows. That is, one is positioned close to the right edge of the middle chassis plate  10 M, and the other is positioned close to the right edge of the left-end chassis plate  10 L. These arrangements are alternately repeated from top to bottom in  FIGS. 2 and 8 . As a result, positions of the fitting portions  26  are staggered, and low-brightness regions are so dispersed that they are not obtrusive in viewing. 
     To hold the set number of light source lamps  3 , the fitting portions  26  are preferably formed at five locations, for example, in the left-end chassis plate  10 L, and at six locations, for example, in the right-end chassis plate  10 R. This breaks the point-symmetry between the left-end and right-end chassis plates  10 L and  10 R, but they can easily be made point-symmetry with each other by adjusting the number of light source lamps  3  such that a same number of fitting portions  26  are formed in the left-end and right-end chassis plates  10 L and  10 R. 
     In this preferred embodiment, a clip  25  holds two light source lamps  3 , but the number of light source lamps  3  that a clip  25  holds is not limited to two. A clip  25  may hold three or more light source lamps  3 , or may hold only one light source lamp  3 . The number of positions in the middle portion of each light source lamp  3  at which it is held is preferably two in this preferred embodiment, but this is not meant to be a limitation, and the number may be set according to the length of the light source lamps  3 . 
     The clip  25  may be fitted by a method other than using the snap pin  25   c  as in this preferred embodiment. For example, a structure is possible in which the clip  25  is adhered to the reflection sheet  2  with a double-stick tape. 
     In this preferred embodiment, the backlight chassis  1  is preferably divided into three chassis plates, but this is merely an example and is not meant to be a limitation. The number of chassis plates into which the backlight chassis  1  is divided may be determined according to the size of the backlight chassis  1 . Division into two chassis plates may be enough with a compact backlight chassis  1 . In addition, the direction of the division-line is not limited to the short-side direction of the backlight chassis  1 . The backlight chassis  1  may be divided along the long-side direction or may be diagonally divided. 
     Next, a second preferred embodiment of the present invention will be described with reference to  FIGS. 11 to 13 .  FIG. 11  is a plan view of a backlight chassis,  FIG. 12  is a sectional view taken along line A-A in  FIG. 11 , and  FIG. 13  is an enlarged partial sectional view of the backlight chassis. 
     One of the unique features of the second preferred embodiment is that the trough-shaped portions  11 L,  11 R, and  11 M in the first preferred embodiment are replaced by trough-shaped members  31 . The trough-shaped members  31  have substantially the same sectional shape as the trough-shaped portions  11 L,  11 R, and  11 M, and have the same length as the trough-shaped portions  11 L,  11 R, and  11 M connected together. 
     In each of the left-end chassis plate  10 L, the right-end chassis plate  10 R, and the middle chassis plate  10 M, on an edge thereof perpendicular or substantially perpendicular to the superposition portions  13  and  14 , which are beam-shaped portions, a rising portion  30  that is similar to the rising portions  12  is formed. The trough-shaped member  31  is so arranged as to cover the rising portion  30 , and to one side wall of the trough-shaped member  31  are connected rising portions  30  of the left-end, right-end, and middle chassis plates  10 L,  10 R, and  10 M. As in the case of connecting the superposition portions  13  and  14  together, screws  21  are preferably used to achieve these connections. 
     In this preferred embodiment, an inner surface of one side wall of the trough-shaped member  31 , that is, a side surface of the trough-shaped member  31  facing a center of the trough-shaped member  31  is superposed on inner side surfaces of the rising portions  30 , that is, side surfaces of the rising portions  30  that face the center of the backlight chassis  1 . The screws  21  are screwed into the rising portions  30  and then into the trough-shaped member  31  to connect them together. In the rising portions  30 , pilot holes are formed to allow easy passage of the screws  21  therethrough, and in the trough-shaped member  31 , pilot holes are formed in which screw grooves are to be formed by tapping. 
     In the other side wall of the trough-shaped member  31 , through holes  32  are formed at positions corresponding to the screws  21  for allowing a driver bit of an unillustrated driver to pass therethrough. Instead of the through holes, a cut may be formed at an edge of the other side wall of the trough-shaped member  31  for allowing a driver bit to pass therethrough. 
     It should be understood that the preferred embodiments specifically described above are not meant to limit the present invention, and that many variations and modifications can be made within the spirit of the present invention. 
     The present invention is widely applicable to a backlight chassis for a large-size liquid crystal display panel. 
     While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims