Abstract:
Disclosed is a display device wherein a light emitting element can have a longer service life, while suppressing luminance unevenness without causing an increase in cost or size. The display device comprises a light guide plate ( 21 ), an LED ( 25 ) that is arranged on the side of at least one corner portion ( 21   d ) of the light guide plate ( 21 ), a frame ( 4 ) that has a lateral portion ( 4   b ), and a bezel ( 5 ) that has a lateral portion ( 5   b ). The LED ( 25 ) is attached to a part ( 4   d ) of the lateral portion ( 4   b ) of the frame ( 4 ), and the part ( 4   d ) is thermally connected to a part ( 5   d ) of the lateral portion ( 5   b ) of the bezel ( 5 ).

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a display device that uses light generated by a light emitting element to perform display operation. 
       BACKGROUND ART 
       [0002]    Conventionally, a light source unit is known which uses an LED (light emitting diode), which is a light emitting element, as a light source. And, such a conventional light unit is disposed in a liquid crystal display device that is a display device, thereby functioning as a backlight unit that illuminates a liquid crystal display panel. In other words, display operation of the liquid crystal display device as a conventional display device is performed by means of light generated by the LED. 
         [0003]    Hereinafter, a structure of the conventional backlight unit, which uses the LED as the light source, is described. Here, there are a direct type of backlight unit and an edge light type backlight unit; the backlight unit described hereinafter is the edge light type. 
         [0004]    The conventional backlight unit, as shown in  FIG. 24 , includes at least: a light guide plate  101  that outputs surface light to a liquid crystal display panel (not shown); and a plurality of LEDs  102  that generate the light which is output from the light guide plate  101 . The light guide plate  101  is substantially rectangular when viewed from its plate-thickness direction and has: a light introduction surface (a surface for introducing light inside)  101   a  that is formed of a predetermined side surface; and a light output surface (a surface for outputting the light introduced inside as surface light to the liquid crystal display panel)  101   b  that is formed of a ceiling surface. Besides, the plurality of LEDs  102  are linearly arranged along the light introduction surface  101   a  of the light guide plate  101  such that each light emitting surface faces the light introduction surface  101   a  of the light guide plate  101 . 
         [0005]    And, in the conventional backlight unit, when light is generated by the plurality of LEDs  102 , the light generated by the plurality of LEDs  102  is introduced from the light introduction surface  101   a  of the light guide plate  101  into an inside of the light guide plate  101 . Thereafter, the light introduced into the inside of the light guide plate  101  turns into surface light and is output from the light output surface  101   b  of the light guide plate  101 . 
         [0006]    Here, although not shown, a reflection sheet is disposed on a rear surface (a surface opposite to the light output surface  101   b ) of the light guide plate  101 , and an optical sheet is disposed on the light output surface  101   b  of the light guide plate  101 . 
         [0007]    In the meantime, in the conventional backlight unit shown in  FIG. 24 , the light generated by the LED  102  travels spreading radially, so that if a distance between adjacent LEDs  102  is large, dark regions (regions marked by hatching in the figure), into which the light spreads only slightly, occur near the light introduction surface  101   a  of the light guide plate  101 , which cause brightness unevenness. As ways of solving this disadvantage, there are: a way of extending a distance between the light introduction surface  101   a  of the light guide plate  101  and the LED  102 ; and a way of increasing the number of LEDs  102  to reduce the distance between the adjacent LEDs  102  (see  FIG. 25 ). However, if these ways are employed, a disadvantage occurs, in which the size becomes large and the cost increases. 
         [0008]    Because of this, conventionally, a backlight unit which is able to solve the above various disadvantages is proposed (e.g., see a patent document 1). Specifically, in the conventional proposed backlight unit, as shown in  FIG. 26 , a side surface of one corner portion of a plurality of corner portions of the light guide plate  101  is inclined with respect to other side surfaces, and the inclined surface of the light guide plate  101  is used as the light introduction surface  101   a.  And, the LED  102  is disposed near the corner portion where the light introduction surface  101   a  of the light guide plate  101  is present. According to this structure, even if only one LED  102  is used and the distance between the light introduction surface  101   a  of the light guide plate  101  and the LED  102  is made small, increase in dark regions (regions marked by hatching in the figure) is curbed. 
       Citation List 
     Patent Literature 
       [0009]    PLT1: JP-A-2006-185852 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0010]    However, in the conventional proposed backlight unit, the light introduction surface  101   a  is formed on the one corner portion of the plurality of corner portions of the light guide plate  101 , and there the LED  102  is disposed to obtain a desired effect; however, measures for radiating heat, which concentrates on the one corner portion of the light guide plate  101  near which the LED  102  is disposed, are not taken. Accordingly, in the conventional proposed backlight unit, the LED  102  deteriorates thanks to heat generated from itself, and as a result of which, there is a problem that life of the LED  102  becomes short. 
       Solution to Problem 
       [0011]    The present invention has been made to solve the above problems, and it is an object of the present invention to provide a display device that is able to achieve a long life of a light emitting element while curbing occurrence of brightness unevenness without causing cost increase and size enlargement. 
         [0012]    To achieve the above object, a display device according to an aspect of the present invention includes: 
         [0013]    a light guide plate that includes a plurality of corner portions; a light emitting element that is disposed near at least one corner portion of the plurality of corner portions of the light guide plate; 
         [0014]    a display panel that is disposed on the light guide plate; 
         [0015]    a first case member that includes: a bottom portion on which the light guide plate is placed; and a first side portion that encloses at least part of a circumference of the light guide plate; and 
         [0016]    a second case member that includes: an upper surface portion that is disposed on the display panel; and a second side portion that encloses at least part of the circumference of the light guide plate. 
         [0017]    And, the light emitting element is disposed near a first portion of the first side portion of the first case member; and the first portion of the first side portion of the first case member is thermally connected to a second portion of the second side portion of the second case member. 
         [0018]    In the display device according to the aspect of the present invention, as described above, the light emitting element is disposed near at least one corner portion of the plurality of corner portions of the light guide plate; accordingly, if an LED, light generated from which travels spreading radially, is used as the light emitting element, it is possible to spread the light into a substantially entire region of an inside of the light guide plate without increasing the number of the light emitting elements and significantly spacing the light emitting element away from the light guide plate. Accordingly, the cost does not increase, the size does not become large, and it is possible to curb occurrence of brightness unevenness. 
         [0019]    And, in the display device according to the aspect, in addition to the above structure, the light emitting element is disposed near the first portion of the first side portion of the first case member, and the first portion of the first side portion of the first case member is thermally connected to the second portion of the second side portion of the second case member, whereby heat conduction from the first portion of the first side portion of the first case member to the second portion of the second side portion of the second case member increases, so that it is possible to easily transmit heat generated from the light emitting element from the first portion of the first side portion of the first case member to the second portion of the second side portion of the second case member. According to this, the heat generated from the light emitting element is efficiently radiated, and it is possible to alleviate the light emitting element being deteriorated by the heat from itself. 
         [0020]    As a result of these, in the display device according to the aspect, it becomes possible to achieve a long life of the light emitting element while curbing occurrence of brightness unevenness without causing cost increase and size enlargement. 
         [0021]    In the display device according to the above aspect, it is preferable that a region enclosed by the first side portion of the first case member includes a plurality of first corner portions; and the first portion of the first side portion of the first case member defines at least one of the plurality of first corner portions of the first case member. According to this structure, by placing the light guide plate on the bottom portion of the first case member such that positions of the plurality of first corner portions of the first case member and positions of the plurality of corner portions of the light guide plate are substantially aligned with each other, it is possible to easily dispose the light emitting element near at least one corner portion of the plurality of corner portions of the light guide plate. 
         [0022]    Besides, in the display device according to the above aspect, it is preferable that a region enclosed by the second side portion of the second case member includes a plurality of second corner portions; and the second portion of the second side portion of the second case member defines at least one of the plurality of second corner portions of the second case member. According to this structure, the first portion of the first side portion of the first case member and the second portion of the second side portion of the second case member both define the corner portions; accordingly, by disposing the first case member and the second case member such that the positions of the first corner portions of the first case member and the positions of the second corner portions of the second case member are substantially aligned with each other, it is easy to thermally connect the first portion of the first side portion of the first case member and the second portion of the second side portion of the second case member to each other. 
         [0023]    In the display device according to the above aspect, it is preferable that the light guide plate includes: a ceiling surface; a rear surface; and a side surface that connects to the ceiling surface and the rear surface; a side surface of the one corner portion of the plurality of corner portions, near which the light emitting element is disposed, is obliquely inclined with respect to another side surface; and the light emitting element is disposed near the first portion of the first side portion of the first case member so as to face the inclined side surface of the light guide plate. According to this structure, it is possible to easily spread the light into the substantially entire region of the inside of the light guide plate. 
         [0024]    In the structure in which the side surface of the corner portion of the light guide plate, near which the light emitting element is disposed, is obliquely inclined with respect to another side surface, it is preferable that the first portion of the first side portion of the first case member includes a tapered shape along the inclined side surface of the light guide plate. According to this structure, by disposing the light emitting element near the first portion of the first side portion of the first case member, it is possible to easily dispose the light emitting element oppositely to the inclined side surface of the light guide plate. Here, the tapered shape is an obliquely inclined shape. 
         [0025]    In the structure in which the first portion of the first side portion of the first case member includes the tapered shape along the inclined side surface of the light guide plate, a heat conductive member may be inserted between the first portion of the first side portion of the first case member and the second portion of the second side portion of the second case member; and the first portion of the first side portion of the first case member and the second portion of the second side portion of the second case member may be thermally connected to each other via the heat conductive member. According to this structure, without making the first portion of the first side portion of the first case member and the second portion of the second side portion of the second case member come into contact with each other, it is possible to thermally connect the first portion of the first side portion of the first case member and the second portion of the second side portion of the second case member to each other. 
         [0026]    Besides, in the structure in which the first portion of the first side portion of the first case member includes the tapered shape along the inclined side surface of the light guide plate, the second portion of the second side portion of the second case member may define a tapered shape that reflects a shape of the first portion of the first side portion of the first case member. According to this structure, it is possible to make the first portion of the first side portion of the first case member and the second portion of the second side portion of the second case member face in parallel with each other, which is preferable when thermally connecting them to each other by making the first portion of the first side portion of the first case member and the second portion of the second side portion of the second case member come into contact with each other. Here, the tapered shape is an obliquely inclined shape. 
         [0027]    In the structure in which the second portion of the second side portion of the second case member defines the tapered shape that reflects the shape of the first portion of the first side portion of the first case member, the second portion of the second side portion of the second case member may be provided thereon with a protrusion portion that protrudes toward the first side portion of the first case member; and the first portion of the first side portion of the first case member and the protrusion portion formed on the second portion of the second side portion of the second case member may be thermally connected to each other. 
         [0028]    Besides, in the structure in which the second portion of the second side portion of the second case member defines the tapered shape that reflects the shape of the first portion of the first side portion of the first case member, the second portion of the second side portion of the second case member may include a spring characteristic; and the second portion of the second side portion of the second case member may be held while biasing the first portion of the first side portion of the first case member. According to this structure, the second portion of the second side portion of the second case member becomes unlikely to go away from the first portion of the first side portion of the first case member, so that it is possible to more surely achieve thermal connection between the first portion of the first side portion of the first case member and the second portion of the second side portion of the second case member. 
         [0029]    In this case, it is preferable that the second portion of the second side portion of the second case member is connected to the upper surface portion, and separated from another portion of the second side portion. According to this structure, the second portion of the second side portion of the second case member becomes displaceable with respect to a border, that is, a fulcrum, with the upper surface portion. According to this, the second portion of the second side portion of the second case member is able to easily have the spring characteristic (a bias force that biases the first portion of the first side portion of the first case member). 
         [0030]    Besides, in the structure in which the second portion of the second side portion of the second case member defines the tapered shape that reflects the shape of the first portion of the first side portion of the first case member, the second portion of the second side portion of the second case member may be fixed, by means of a screw, to the first portion of the first side portion of the first case member. According to this structure, it is possible to easily and surely connect thermally the first side portion of the first case member and the second side portion of the second case member to each other. 
         [0031]    In the display device according to the above aspect, it is preferable that the first case member and the second case member are each formed of a metal. According to this structure, it is possible to efficiently radiate the heat generated from the light emitting element. 
       Advantageous Effects of Invention 
       [0032]    As described above, according to the present invention, it is easy to obtain a display device that is able to achieve a long life of the light emitting element while curbing occurrence of brightness unevenness without causing cost increase and size enlargement. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0033]    [ FIG. 1 ] is an exploded perspective view of a liquid crystal display device according to a first embodiment. 
           [0034]    [ FIG. 2 ] is a plan view (a view with a reflection sheet and an optical sheet omitted) of a backlight unit that is disposed in the liquid crystal display device according to the first embodiment. 
           [0035]    [ FIG. 3 ] is a sectional view of a backlight unit that is disposed in the liquid crystal display device according to the first embodiment. 
           [0036]    [ FIG. 4 ] is a view for describing structures of a frame and a bezel of the liquid crystal display device according to the first embodiment. 
           [0037]    [ FIG. 5 ] is an enlarged view of part (a portion where an LED is situated) of  FIG. 4 . 
           [0038]    [ FIG. 6 ] is a view for describing behavior of light in an inside of a light guide plate. 
           [0039]    [ FIG. 7 ] is a view for describing behavior of light in an inside of a light guide plate. 
           [0040]    [ FIG. 8 ] is a view for describing behavior of light in an inside of a light guide plate. 
           [0041]    [ FIG. 9 ] is a view in a case where brightness unevenness is reduced by enlarging a light guide plate. 
           [0042]    [ FIG. 10 ] is a view for describing structures of a frame and a bezel of a liquid crystal display device according to a second embodiment. 
           [0043]    [ FIG. 11 ] is an enlarged view of part (a portion where an LED is situated) of  FIG. 10 . 
           [0044]    [ FIG. 12 ] is an enlarged perspective view of a portion of a corner portion of the bezel shown in  FIG. 10 . 
           [0045]    [ FIG. 13 ] is a view (an enlarged view of a portion where an LED is situated) for describing structures of a frame and a bezel of a liquid crystal display device according to a modification of the second embodiment. 
           [0046]    [ FIG. 14 ] is a view (an enlarged view of a portion where an LED is situated) for describing structures of a frame and a bezel of a liquid crystal display device according to a modification of the second embodiment. 
           [0047]    [ FIG. 15 ] is a view for describing structures of a frame and a bezel of a liquid crystal display device according to a third embodiment. 
           [0048]    [ FIG. 16 ] is an enlarged view of part (a portion where an LED is situated) of  FIG. 15 . 
           [0049]    [ FIG. 17 ] is an enlarged perspective view of a portion of a corner portion of the bezel shown in  FIG. 15 . 
           [0050]    [ FIG. 18 ] is an enlarged sectional view of a portion of a corner portion of the bezel shown in  FIG. 15 . 
           [0051]    [ FIG. 19 ] is a sectional view when a frame is disposed on the bezel shown in  FIG. 18 . 
           [0052]    [ FIG. 20 ] is a view (an enlarged view of a portion where an LED is situated) for describing structures of a frame and a bezel of a liquid crystal display device according to a modification of the third embodiment. 
           [0053]    [ FIG. 21 ] is an enlarged perspective view of a portion of a corner portion of the bezel shown in  FIG. 20 . 
           [0054]    [ FIG. 22 ] is an enlarged view of a portion where an LED of a liquid crystal display device according to a modification of the present invention is situated. 
           [0055]    [ FIG. 23 ] is an enlarged view of a portion where an LED of a liquid crystal display device according to a modification of the present invention is situated. 
           [0056]    [ FIG. 24 ] is a view simply describing a conventional backlight unit. 
           [0057]    [ FIG. 25 ] is a view simply describing a conventional backlight unit. 
           [0058]    [ FIG. 26 ] is a view simply describing a conventional proposed backlight unit. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
     First Embodiment 
       [0059]    First, a structure of a display device according to a first embodiment is described with reference to  FIG. 1  to  FIG. 5 . 
         [0060]    The display device according to the first embodiment is a liquid crystal display device that, as shown in  FIG. 1 , includes: a liquid crystal display panel  1  that has a display surface  1   a ; an edge light type of backlight unit  2  that is disposed on a rear surface (a surface opposite to the display surface) of the liquid crystal display panel  1  and others. Here, the liquid crystal display panel  1  is an example of a “display panel” of the present invention. 
         [0061]    The liquid crystal display panel  1  according to the first embodiment includes at least: a liquid crystal layer (not shown); a pair of glass boards  11  that sandwich the liquid crystal layer; and two light polarization plates  12  that are each disposed on a surface of the pair of glass boards  11  opposite to the liquid crystal layer. Here, in  FIG. 1 , of the two light polarization plates  12 , only the light polarization plate  12  facing the display surface la of the liquid crystal display panel  1  is shown. Besides, a drive circuit  13  for driving a thin film transistor (not shown) formed on one of the pair of glass boards  11  is connected to the one of the pair of glass boards  11 . 
         [0062]    Besides, the backlight unit  2  in the first embodiment, as shown in  FIG. 1  to  FIG. 3 , includes at least: a light guide plate  21 ; an LED module  22 ; a reflection sheet  23 ; and an optical sheet  24 . Here, in  FIG. 2 , for clear understanding of the figure, the reflection sheet  23  and the optical sheet  24  are not shown. 
         [0063]    The light guide plate  21  is formed of a light-transmissive plate member and has a function to change light introduced in its inside into surface light and output the surface light to the liquid crystal display panel  1 . As a specific structure, the light guide plate  21  includes: a ceiling surface  21   a;  a rear surface  21   b  that is a surface opposite to the ceiling surface  21   a;  and a side surface  21   c  that connects to the ceiling surface  21   a  and the rear surface  21   b.  And, in a state where the backlight unit  2  is disposed to the rear side of the liquid crystal display panel  1 , the ceiling surface  21   a  of the light guide plate  21  faces the liquid crystal display panel  1 . In other words, the ceiling surface  21   a  of the light guide plate  21  defines a light output surface (a surface for outputting the light introduced in the inside to the liquid crystal display panel  1 ). 
         [0064]    Besides, when viewing the light guide plate  21  from a plate thickness direction, the light guide plate  21  defines a shape (a substantially rectangular shape) that has four corner portions  21   d;  of the four corner portions  21   d,  side surfaces  21   c  of two corner portions  21   d  that are situated at both ends (each one end of a pair of short edges) of one long edge are obliquely inclined with respect to the other side surfaces  21   c.  And, in the first embodiment, of the side surfaces  21   c  of the light guide plate  21 , the inclined two side surfaces  21   c  (hereinafter, called inclined surfaces  21   e ) are used as light introduction surfaces (surfaces for introducing the light into the inside). Each of the two inclined surfaces  21   e  of the light guide plate  21  has an inclination angle of about 45° and is finished to be a mirror surface. 
         [0065]    The LED module  22  has an LED  25  as a light emitting element disposed on an FPC (flexible printed circuit)  26 , and functions as a light source that generates the light introduced into the inside of the light guide plate  21 . In other words, the LED module  22  is disposed along one long edge of the light guide plate  21  such that a light emitting surface of the LED  25  faces the inclined surface  21   e  of the light guide plate  21 . 
         [0066]    Here, in the first embodiment, two LEDs  25  are used and are each disposed on two regions that face the inclined surfaces  21   e  of the light guide plate  21 . Besides, the two LEDs  25  are disposed on the same FPC  26  and the FPC  26  is bent along the side surface  21   c  (which includes the two inclined surfaces  21   e ) of the one long edge of the light guide plate  21 . In other words, both ends of the FPC  26  respectively face the two inclined surfaces  21   e  of the light guide plate  21 ; and a portion between both the ends of the FPC  26  faces a not-inclined side surface (a side surface between the two inclined surfaces  21   e ) of the light guide plate  21 . And, the LEDs  25  are each disposed on both the ends of the FPC  26 . 
         [0067]    Besides, the reflection sheet  23  is disposed on the rear surface  21   b  of the light guide plate  21  and covers the entire surface of the rear surface  21   b  of the light guide plate  21 . By disposing the reflection sheet  23 , the rear surface  21   b  of the light guide plate  21  defines a reflection surface, so that light leak from the rear surface  21   b  of the light guide plate  21  is curbed and light use efficiency increases. 
         [0068]    The optical sheet  24  is disposed on the ceiling surface  21   a  of the light guide plate  21  and covers the entire surface of the ceiling surface  21   b  of the light guide plate  21 . The optical sheet  24  has a plurality of sheets (a diffusion sheet, a prism sheet and others) stacked on one another, and performs diffusion and collection of the light output from the ceiling surface  21   a  of the light guide plate  21 . And, the liquid crystal display panel  1  is illuminated with the light that is diffused and collected by the optical sheet  24 . Here, in  FIG. 1  and  FIG. 3 , the optical sheet  24 , which has three sheets stacked on one another, is shown; however, the number of sheets is not especially limited. 
         [0069]    Besides, as shown in  FIG. 1 , a rectangular plastic frame  3  is disposed between the liquid crystal display panel  1  and the backlight unit  2 . And, an outer edge of the optical sheet  24  is pushed against an edge portion of the plastic frame  3  so as to hold a stacked body which includes the reflection sheet  23 , the light guide plate  21  and the optical sheet  24  that are stacked in this order. 
         [0070]    Besides, the liquid crystal display panel  1  and the backlight unit  2  are sandwiched by the frame  4  on the rear surface side and the bezel  5  on the ceiling surface side. Here, the frame  4  is an example of a “first case member” of the present invention and the bezel  5  is an example of a “second case member” of the present invention. 
         [0071]    The frame  4  is formed of a metal and obtained by deforming a plate member formed of aluminum, iron or the like. The frame  4  includes: a bottom portion  4   a;  and a side portion  4   b  formed vertically on an outer circumference of the bottom portion  4   a , and is formed such that a region enclosed by the four side portions  4   b  defines a substantially rectangular shape that has four corner portions  4   c.  And, the region enclosed by the side portions  4   b  on the bottom portion  4   a  of the frame  4  is used as a housing region. Here, the side portion  4   b  of the frame  4  is an example of a “first side portion” of the present invention and the corner portion  4   c  is an example of a “first corner portion” of the present invention. 
         [0072]    The constituent members ( 21  to  24 ) of the backlight unit  2  are housed in the housing region; of these, the reflection sheet  23 , the light guide plate  21  and the optical sheet  24  are stacked in this order on the bottom portion  4   a  of the frame  4 . Here, in this state, the rear surface  21   b  (see  FIG. 3 ) of the light guide plate  21  faces the bottom surface  4   a  of the frame  4 , while the side surface  21   c  (see  FIG. 2 ), which includes the two inclined surfaces  21   e  of the light guide plate  21 , faces the side portion  4   b  of the frame  4 . Further, the respective long edges (short edges) of the light guide plate  21  and of the frame  4  are parallel with each other; and positions of the corner portions  21   d  of the light guide plate  21  and positions of the four corner portions  4   c  of the frame  4  are substantially aligned with each other. 
         [0073]    Besides, as shown in  FIG. 1  and  FIG. 4 , near two corner portions  4   c  of the four corner portions  4   c  of the frame  4 , the inclined surfaces  21   e  of the light guide plate  21  are each disposed; two portions (first portions)  4   d  of the side portion  4   b  of the frame  4 , which define the two corner portions  4   c,  are formed to be a tapered shape that has an inner surface along the inclined surface  21   e  of the light guide plate  21 . In other words, the side portion  4   a  (which includes the two portions  4   d ) of one long edge of the frame  4  is bent along the side surface  21   c  (which includes the two inclined surfaces  21   e ) of one long edge of the light guide plate  21 . And, the LED module  22  is disposed along an inner side surface of the side portion  4   b  of the one long edge of the frame  4 , whereby the LEDs  25  are each disposed near the two portions  4   d  of the side portion  4   b  of the frame  4 , and the light emission surface of each of the two LEDs  25  faces the corresponding inclined surface  21   e  of the light guide plate  21 . Here, the two other corner portions  4   c  of the frame  4  are each formed to be a substantially rectangular shape. 
         [0074]    The bezel  5 , which collaborates with the frame  4  to sandwich the liquid crystal display panel  1  and the backlight unit  2 , is obtained by deforming a plate member formed of stainless steel, iron or the like, and includes: a frame-shaped upper surface portion  5   a;  and a side portion  5   b  formed vertically on an outer circumference of the upper surface portion  5   a.  Besides, a region enclosed by the side portion  5   b  of the bezel  5  defines a substantially rectangular shape that has four corner portions  5   c,  and each of the four corner portions  5   c  of the bezel  5  is formed to be a rectangular or substantially rectangular shape. Here, the side portion  5   b  of the bezel  5  is an example of a “second side portion” of the present invention and the corner portion  5   c  is an example of a “second corner portion” of the present invention. 
         [0075]    And, in the state where the bezel  5  collaborates with the frame  4  to sandwich the liquid crystal display panel  1  and the backlight unit  2 , the upper surface portion  5   a  of the bezel  5  covers an outer edge of the display surface  1   a  of the liquid crystal display panel  1 . Besides, the side portion  5   b  of the bezel  5  is disposed along an outer surface of the side portion  4   b  of the frame  4 , thereby overlying the side portion  4   b  of the frame  4 . Further, the respective long edges (short edges) of the bezel  5  and of the frame  4  are parallel with each other; and positions of the four corner portions  5   c  of the bezel  5  and positions of the four corner portions  4   c  of the frame  4  are substantially aligned with each other. 
         [0076]    Here, in the first embodiment, when viewing each of the two corner portions  4   c  (two corner portions  5   c  of the bezel  5 ) of the frame  4  near which the LEDs  25  are situated, the portion (the portion near which the LED  25  is disposed)  4   d  of the side portion  4   b  of the frame  4  is thermally connected to a portion (second portion)  5   d  that is a portion of the side portions  5   b  of the bezel  5  and defines the corner portion  5   c.    
         [0077]    Specifically, as shown in  FIG. 4  and  FIG. 5 , when viewing each of the two corner portions  4   c  (the two corner portions  5   c  of the bezel  5 ) of the frame  4  near which the LEDs  25  are situated, the portion  4   d  of the side portion  4   b  of the frame  4  is tapered, so that a triangular gap is formed between the portion  4   d  of the side portion  4   b  of the frame  4  and the portion  5   d  of the side portion  5   b  of the bezel  5 . Because of this, in the first embodiment, a heat conductive member  6  is buried in the triangular gap between the portion  4   d  of the side portion  4   b  of the frame  4  and the portion  5   d  of the side portion  5   b  of the bezel  5 , whereby the heat conductive member  6  is made to come into contact with each of the portion  4   d  of the side portion  4   b  of the frame  4  and the portion  5   d  of the side portion  5   b  of the bezel  5 . In other words, the outer surface of the portion  4   d  of the side portion  4   b  of the frame  4  and the inner surface of the portion  5   d  of the side portion  5   b  of the bezel  5  are thermally connected to each other via the heat conductive member  6 . 
         [0078]    Here, as a material of the heat conductive member  6 , there is a resin heat radiation sheet formed of silicone rubber or the like. Besides, as a method for fixing the heat conductive member  6 , it is sufficient to simply insert the heat conductive member  6  into the triangular gap between the portion  4   d  of the side portion  4   b  of the frame  4  and the portion  5   d  of the side portion  5   b  of the bezel  5 ; however, it is more preferable to adhere the heat conductive member  6  to the inner surface of the portion  5   d  of the side portion  5   b  of the bezel  5  by means of double-coated tape or the like. 
         [0079]    In the first embodiment, as described above, the LED  25  is disposed near the inner surface of the portion  4   d  that is a portion of the side portion  4   b  of the frame  4  and defines a predetermined corner portion (a corner portion near which the inclined surface  21   e  of the light guide plate  21  is disposed); and the outer surface of the portion  4   d  of the side portion  4   b  of the frame  4  is thermally connected to the portion  5   d  of the side portion  5   b  of the bezel  5 , whereby heat conduction from the portion  4   d  of the side portion  4   b  of the frame  4  to the portion  5   d  of the side portion  5   b  of the bezel  5  increases, so that it is possible to easily transmit heat generated from the portion  4   d  of the side portion  4   b  of the frame  4  to the side portion  5   b  of the bezel  5 . According to this, the heat generated from the LED  25  is efficiently radiated, and it is possible to alleviate the LED  25  being deteriorated by the heat from itself. 
         [0080]    Further, in addition to this, the side surfaces  21   c  of the two corner portions  21   d  of the four corner portions  21   d  of the light guide plate  21  are inclined, and the LEDs  25  are each disposed so as to face each of the two inclined surfaces of the light guide plate  21 , so that the light from one of the LEDs  25  spreads in the inside of the light guide plate  21  as shown in  FIG. 6 , while the light from the other of the LEDs  25  spreads in the inside of the light guide plate  21  as shown in  FIG. 7 . Because of this, as shown in  FIG. 8 , the light spreads into the substantially entire region of the inside of the light guide plate  21 , and the dark region into which the light is unlikely to spread becomes less than conventional. According to this, it is possible to output the surface light, which has less brightness unevenness, from the backlight unit  2 . Here, in  FIG. 6  to  FIG. 8 , regions marked by hatching are dark regions, and the other regions are regions into which the light spreads. 
         [0081]    As a result of these, in the first embodiment, it becomes easy to achieve a long life of the LED  25  while curbing occurrence of brightness unevenness without causing cost increase and size enlargement. 
         [0082]    In the meantime, to achieve further reduction of the brightness unevenness by disposing the LED at only one corner portion of the four corner portions of the light guide plate, it is necessary to produce a light guide plate  121  that has a shape as shown in  FIG. 9 . In other words, light from an LED  125  spreads into an angle range of about ±42° only; accordingly, to spread the light from the LED  125  into a substantially entire region of an effective light emission area (a region enclosed by a broken line), it is necessary to significantly space a light introduction surface  121   e  of the light guide plate  121  away from the effective light emission area. Because of this, even if it is possible to achieve further reduction of the brightness unevenness, size enlargement is caused. 
         [0083]    Besides, in the first embodiment, as described above, the portion  4   d,  which is a portion of the side portion  4   b  of the frame  4  and defines the predetermined corner portion  4   c,  is used as the disposition portion at which the LED  2  is disposed; and the light guide plate  21  is placed on the bottom portion  4   a  of the frame  4  such that the positions of the four corner portions  4   c  of the frame  4  and the positions of the four corner portions  21   d  of the light guide plate  21  are substantially aligned with each other, so that it is easy to dispose the LED  25  such that the LED  25  faces the inclined surface  21   e  of the light guide plate  21 . 
         [0084]    Besides, in the first embodiment, as described above, the portion  5   d,  which defines the predetermined corner portion  5   c  (the portion near which the LED  25  is situated) of the side portion  5   b  of the bezel  5 , is used as the portion for the thermal connection with the portion (the portion near which the LED  25  is disposed)  4   d  of the side portion  4   b  of the frame  4 , whereby the portion  4   d  of the side portion  4   b  of the frame  4  and the portion  5   d  of the side portion  5   b  of the bezel  5  both define the corner portions; accordingly, by disposing the frame  4  and the bezel  5  such that the position of the corner portion  4   c  of the frame  4  and the position of the corner portion  5   c  of the bezel  5  are substantially aligned with each other, it is easy to thermally connect the portion  4   d  of the side portion  4   b  of the frame  4  and the portion  5   d  of the side portion  5   b  of the bezel  5  to each other. 
         [0085]    Besides, in the first embodiment, as described above, the portion  4   d  of the side portion  4   b  of the frame  4  is formed to be the tapered shape that has the inner surface along the inclined surface  21   e  of the light guide plate  21 ; accordingly, by disposing the LED  25  at the inner surface of the portion  4   d  of the side portion  4   b  of the frame  4 , so that it is easy to dispose the LED  25  such that the LED  25  faces the inclined surface  21   e  of the light guide plate  21 . 
         [0086]    Besides, in the first embodiment, as described above, the heat conductive member  6  is inserted between the portion  4   d  of the side portion  4   b  of the frame  4  and the portion  5   d  of the side portion  5   b  of the bezel  5 ; accordingly, even if the portion  4   d  of the side portion  4   b  of the frame  4  and the portion  5   d  of the side portion  5   b  of the bezel  5  are not made to directly come into contact with each other, it is possible to thermally connect the portion  4   d  of the side portion  4   b  of the frame  4  and the portion  5   d  of the side portion  5   b  of the bezel  5  to each other. 
       Second Embodiment 
       [0087]    Hereinafter, a structure of a display device according to a second embodiment is described with reference to  FIG. 10  to  FIG. 12 . 
         [0088]    The display device (liquid crystal display device) according to the second embodiment uses a metal bezel (second case member)  35  shown in  FIG. 10  to  FIG. 12  is used, but has the same structure as the first embodiment except that such bezel  35  is used. 
         [0089]    The bezel  35 , like the bezel  5  in the above first embodiment, includes: a frame-shaped upper surface portion  35   a;  and a side portion (second side portion)  35   b  formed vertically on an outer circumference of the upper surface portion  35   a;  and a region enclosed by the side portion  35   b  is formed to be a substantially rectangular shape that has four corner portions (second corner portion)  35   c.  And, in a state where the bezel  35  collaborates with the frame  4  to sandwich the liquid crystal display panel  1  and the backlight unit  2 , the respective long edges (short edges) of the bezel  35  and the frame  4  are parallel with each other; and positions of the four corner portions  35   c  of the bezel  35  and positions of the four corner portions  4   c  of the frame  4  are substantially aligned with each other. Besides, the side portion  35   b  of the bezel  35  is situated along the outer surface of the side portion  4   b  of the frame  4 . 
         [0090]    Here, in the second embodiment, the inclined surfaces  21   e  of the light guide plate  21  are each disposed near two corner portions  35   c  of the four corner portions  35   c  of the bezel  35 ; and two portions  35   d,  which are portions of the side portion  35   b  of the bezel  35  and define the two side portions  35   c,  are each formed to be a tapered shape (a shape along the inclined surface  21   e  of the light guide plate  21 ). In other words, when viewing each of the two corner portions  4   c  (the two corner portions  35   c  of the bezel  35 ) of the frame  4  near which the LEDs  25  are situated, the portion  4   d  of the side portion  4   b  of the frame  4  and the portion  35   d  of the side portion  35   b  of the bezel  35  both are tapered; and the shape of the portion  35   d  of the side portion  35   b  of the bezel  35  reflect the shape of the portion  4   d  of the side portion  4   b  of the frame  4 . Here, each of the two other corner portions  35   c  of the bezel  35  is formed to be a substantially rectangular shape. 
         [0091]    Besides, in the second embodiment, when viewing each of the two corner portions  4   c  (the two corner portions  35   c  of the bezel  35 ) of the frame  4  at which the LEDs  25  are situated, the portion  35   d  of the side portion  35   b  of the bezel  35  is provided thereon with a circular protrusion portion  35   e  that protrudes toward the portion  4   d  of the side portion  4   b  of the frame  4 . Here, for example, the protrusion portion  35   e  formed on the portion  35   d  of the side portion  35   b  of the bezel  35  is obtained by applying draw forming to a metal plate member that forms the bezel  35 . 
         [0092]    And, in the second embodiment, at each of the two corner portions  4   c  (the two corner portions  35   c  of the bezel  35 ) of the frame  4  at which the LEDs  25  are situated, the protrusion portion  35   e  formed on the portion  35   d  of the side portion  35   b  of the bezel  35  directly thermally comes into contact with the outer surface of the portion  4   d  of the side portion  4   b  of the frame  4 , so that the portion  4   d  of the side portion  4   b  of the frame  4  and the portion  35   d  (protrusion portion  35   e ) of the side portion  35   b  of the bezel  35  are thermally connected to each other. 
         [0093]    In the second embodiment, according to the above structure, it becomes possible to obtain the same effect as the first embodiment. 
         [0094]    Besides, in the second embodiment, as described above, the portion  35   d  of the side portion  35   b  of the bezel  35  is formed to be the tapered shape that reflects the shape of the portion  4   d  of the side portion  4   b  of the frame  4 , so that the portion  4   d  of the side portion  4   b  of the frame  4  and the portion  35   d  of the side portion  35   b  of the bezel  35  face in parallel with each other, which is preferable when thermally connecting them to each other by making the portion  4   d  of the side portion  4   b  of the frame  4  and the portion  35   d  of the side portion  35   b  of the bezel  35  come into contact with each other. 
         [0095]    Further, in the second embodiment, as described above, the portion  35   d  of the side portion  35   b  of the bezel  35  is provided thereon with the circular protrusion portion  35   e  that protrudes toward the portion  4   d  of the side portion  4   b  of the frame  4 , so that it is possible to surely maintain the state where the portion  4   d  of the side portion  4   b  of the frame  4  and the portion  35   d  of the side portion  35   b  of the bezel  35  are in direct contact with each other. In other words, it is possible to surely achieve the thermal contact between the portion  4   d  of the side portion  4   b  of the frame  4  and the portion  35   d  of the side portion  35   b  of the bezel  35 . 
         [0096]    Here, in the structure according to the second embodiment, the protrusion portion  35   e  formed on the portion  35   d  of the side portion  35   b  of the bezel  35  is not especially limited; for example, although not shown, a linear-shape protrusion portion may be formed on the portion  35   d  of the side portion  35   b  of the bezel  35 . 
         [0097]    Besides, in the structure according to the second embodiment, as shown in  FIG. 13 , the protrusion portion may not be formed on the portion  35   d  of the side portion  35   b  of the bezel  35 , but a heat conductive member  36  may be inserted between the portion  4   d  of the side portion  4   b  of the frame  4  and the portion  35   d  of the side portion  35   b  of the bezel  35 . 
         [0098]    Besides, in the structure according to the second embodiment, as shown in  FIG. 14 , the protrusion portion may not be formed on the portion  35   d  of the side portion  35   b  of the bezel  35 , but the portion  35   d  of the side portion  35   b  of the bezel  35  may be fixed, by means of a screw, to the portion  4   d  of the side portion  4   b  of the frame  4 , whereby the portion  4   d  of the side portion  4   b  of the frame  4  and the portion  35   d  of the side portion  35   b  of the bezel  35  may be forcibly made to come into contact with each other. In this case, it is possible to easily and surely connect thermally the portion  4   d  of the side portion  4   b  of the frame  4  and the portion  35   d  of the side portion  35   b  of the bezel  35  to each other. 
       Third Embodiment 
       [0099]    Hereinafter, a structure of a display device according to a third embodiment is described with reference to  FIG. 15  to  FIG. 19 . 
         [0100]    The display device (liquid crystal display device) according to the third embodiment uses a metal bezel (second case member)  45  shown in  FIG. 15  to  FIG. 17  is used, but has the same structure as the first embodiment except that such bezel  45  is used. 
         [0101]    The bezel  45 , like the bezel  5  in the above first embodiment, includes: a frame-shaped upper surface portion  45   a;  and a side portion (second side portion)  45   b  formed vertically on an outer circumference of the upper surface portion  45   a;  and a region enclosed by the side portion  45   b  is formed to be a substantially rectangular shape that has four corner portions (second corner portion)  45   c.  And, in a state where the bezel  45  collaborates with the frame  4  to sandwich the liquid crystal display panel  1  and the backlight unit  2 , the respective long edges (short edges) of the bezel  45  and the frame  4  are parallel with each other; and positions of the four corner portions  45   c  of the bezel  45  and positions of the four corner portions  4   c  of the frame  4  are substantially aligned with each other. Besides, the side portion  45   b  of the bezel  45  is situated along the outer surface of the side portion  4   b  of the frame  4 . 
         [0102]    Here, in the third embodiment, the inclined surfaces  21   e  of the light guide plate  21  are each disposed near two corner portions  45   c  of the four corner portions  45   c  of the bezel  45 ; and two portions  45   d,  which are portions of the side portion  45   b  of the bezel  45  and define the two side portions  45   c,  are each formed to be a tapered shape (a shape along the inclined surface  21   e  of the light guide plate  21 ). In other words, when viewing each of the two corner portions  4   c  (the two corner portions  45   c  of the bezel  45 ) of the frame  4  near which the LEDs  25  are situated, the portion  4   d  of the side portion  4   b  of the frame  4  and the portion  45   d  of the side portion  45   b  of the bezel  45  both are tapered; and the shape of the portion  45   d  of the side portion  45   b  of the bezel  45  reflect the shape of the portion  4   d  of the side portion  4   b  of the frame  4 . Here, each of the two other corner portions  45   c  of the bezel  45  is formed to be a substantially rectangular shape. 
         [0103]    Further, in the third embodiment, when viewing each of the two corner portions  4   c  (the two corner portions  45   c  of the bezel  45 ) of the frame  4  near which the LEDs  25  are situated, the portion  45   d  of the side portion  45   b  of the bezel  45  is connected to the upper surface portion  45   a,  and separated from other portions (portions other than the portion  45   d ) of the side portion  45   b.  In other words, slits  45   f  are formed between the portion  45   d  of the side portion  45   b  of the bezel  45  and the other portions; because of this, the portion  45   d  of the side portion  45   b  of the bezel  45  is displaceable with respect to a border, that is, a fulcrum, with the upper surface portion  45   a.    
         [0104]    And, in the third embodiment, as shown in  FIG. 18  and  FIG. 19 , at each of the two corner portions  4   c  (the two corner portions  45   c  of the bezel  45 ) of the frame  4  near which the LEDs  25  are situated, the portion  45   d  of the side portion  45   b  of the bezel  45  is inclined in an X direction in advance; when disposing the bezel  45 , the portion  45   d  of the side portion  45   b  is elastically deformed, whereby the side portion  45   b  of the bezel  45  is disposed on the outer surface side of the of the side portion  4   b  of the frame  4 . According to this, the portion  45   d  of the side portion  45   b  of the bezel  45  is held while biasing (pushing) the portion  4   d  of the side portion  4   b  of the frame  4 ; and as a result, the portion  45   d  of the side portion  45   b  of the bezel  45  is thermally directly connected to the portion  4   d  of the side portion  4   b  of the frame  4 . 
         [0105]    In the third embodiment, according to the above structure, it becomes possible to obtain the same effect as the first embodiment. 
         [0106]    Besides, in the third embodiment, as described above, the portion  4   d  of the side portion  4   b  of the frame  4  and the portion  45   d  of the side portion  45   b  of the bezel  45  face each other; and the portion  45   d  of the side portion  45   b  of the bezel  45  biases and holds the portion  4   d  of the side portion  4   b  of the frame  4 , whereby the portion  45   d  of the side portion  45   b  of the bezel  45  becomes unlikely to go away from the portion  4   d  of the side portion  4   b  of the frame  4 , so that it is possible to more surely achieve thermal connection between the portion  4   d  of the side portion  4   b  of the frame  4  and the portion  45   d  of the side portion  45   b  of the bezel  45 . 
         [0107]    In this case, the portion  45   d  of the side portion  45   b  of the bezel  45  is connected to the upper surface portion  45   a,  and separated from the other portions (portions other than the portion  45   d ) of the side portion  45   b,  whereby the portion  45   d  of the side portion  45   b  of the bezel  45  is displaceable with respect to the border, that is, the fulcrum, with the upper surface portion  45   a,  so that the portion  45   d  of the side portion  45   b  of the bezel  45  is easily able to have a spring characteristic (a bias force that biases the portion  4   d  of the side portion  4   b  of the frame  4 ). 
         [0108]    Here, in the structure according to the third embodiment, although not shown, the portion  45   d  of the side portion  45   b  of the bezel  45  may be designed so as to come to an inner position. 
         [0109]    Besides, in the structure according to the third embodiment, as shown in  FIG. 20  and  FIG. 21 , a protrusion portion  45   e  may be formed on the portion  45   d  of the side portion  435   b  of the bezel  45 ; and the protrusion portion  45   e  formed on the portion  45   d  of the side portion  435   b  of the bezel  45  may be made to directly come into contact with the outer surface of the portion  4   d  of the side portion  4   b  of the frame  4 . In other words, the structure according to the third embodiment and the structure according to the second embodiment may be combined with each other. 
         [0110]    Here, it should be understood that the embodiments disclosed this time are examples in all respects and not limiting. The scope of the present invention is not indicated by the above description of the embodiments but by the claims, and all modifications within the scope of the claims and the meaning equivalent to the claims are covered. 
         [0111]    For example, in the above embodiments, the LED is disposed near each of the two corner portions of the four corner portions of the light guide plate; however, the present invention is not limited to this, and the LED may be disposed near each of three corner portions of the four corner portions of the light guide plate. In other words, three or more corner portions of the four corner portions of the light guide plate may be formed to be inclined surfaces; and each of the three or more inclined surfaces may be made to function as the light introduction surface. According to this structure, the dark region becomes smaller, and it is possible to further reduce occurrence of brightness unevenness. Besides, the LED may be disposed near only one corner portion of the four corner portions of the light guide plate. 
         [0112]    Besides, in the above embodiments, one LED is disposed near one inclined surface (light introduction surface) of the light guide plate; however, the present invention is not limited to this, and a plurality of LEDs may be disposed near one inclined surface of the light guide plate. For example, describing the structure according to the above third embodiment as an example, as shown in  FIG. 22 , two LEDs  25  may be disposed so as to face one inclined surface (light guide plate)  21   e  of the light guide plate  21 . 
         [0113]    Besides, in the above embodiments, one inclined surface (light introduction surface) is formed on one corner portion of the light guide plate; however, the present invention is not limited to this, and a plurality of inclined surfaces having inclination angles different from each other may be formed on one corner portion of the light guide plate; and the LED may be disposed near each of the plurality of inclined surfaces. In other words, the light introduction surface may have a multi-surface structure. For example, describing the structure according to the above third embodiment as an example, as shown in  FIG. 23 , three inclined surfaces (light introduction surface)  21   e  may be formed on one corner portion  21   d  of the light guide plate  21 ; and one LED  25  may be disposed near each of the three inclined surfaces  21   e . Here, in this case, it is preferable that the portion  4   d  of the side portion  4   b  of the frame  4  is formed to be a shape along the three inclined surfaces  21   e  of the light guide plate  21 ; and the portion  45   d  of the side portion  45   b  of the bezel  45  is formed to be a shape along the portion  4   d  of the side portion  4   b  of the frame  4 . 
       REFERENCE SIGNS LIST 
       [0114]      1  liquid crystal display panel (display panel) 
         [0115]      1   a  display surface 
         [0116]      2  backlight unit 
         [0117]      4  frame (first case member) 
         [0118]      4   a  bottom portion 
         [0119]      4   b  side portion (first side portion) 
         [0120]      4   c  corner portion (first corner portion) 
         [0121]      4   d  portion (first portion) 
         [0122]      5 ,  35 ,  45  bezel (second case member) 
         [0123]      5   a,    35   a,    45   a  upper surface portion 
         [0124]      5   b,    35   b,    45   b  side portion (first side portion) 
         [0125]      5   c,    35   c,    45   c  corner portion (second corner portion) 
         [0126]      5   d,    35   d,    45   d  portion (second portion) 
         [0127]      6 ,  36  heat conductive member 
         [0128]      21  light guide plate 
         [0129]      21   a  ceiling surface 
         [0130]      21   b  rear surface 
         [0131]      21   c  side surface 
         [0132]      21   d  corner portion 
         [0133]      21   e  inclined surface 
         [0134]      25  LED (light emitting element) 
         [0135]      35   e,    45   e  protrusion portion 
         [0136]      37  screw 
         [0137]      45   f  slit