Abstract:
A diffusion plate (DL) allowing the light from a fluorescent tube ( 71 ) to transmit therethrough is held on a support surface ( 1 S,  1 S) forming one surface of a side holder (SF). In particular, a support frame (FM) which also plays the role of the side holder (SF) supports the diffusion plate (DL) of a shape of which the long dimension and short dimension parts can be defined, for example, a rectangular shape at only two short dimension parts on its outer edges opposed to each other.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a backlight unit that emits light and to a liquid crystal display that uses the light from the backlight unit. 
     2. Background Art 
     Conventionally, in a backlight unit of a liquid crystal display, a diffusion plate is incorporated, and a prism sheet (lens sheet) for improving light collection capability is disposed on the diffusion plate. In such a backlight unit, there has been a problem of deformation of resin members (a diffusion plate, a lens sheet and the like) which is caused by heat of a light source, especially, deformation of the resin members that is caused by heat conducted according to on/off of the light source or heat radiation. This is because a squeak sound is generated by contact between a bent diffusion plate and the like and other members if such deformation (bend) occurs. 
     As a backlight unit that solves such problem, there is a backlight unit  182  that is disclosed in a patent document 1 and shown in  FIG. 26 . The backlight unit  182  sandwiches a relatively thin diffusion sheet  192  and a lens sheet SS′ located to cover the diffusion sheet  192  between a light guide plate  191  and a relatively thick diffusion plate DL′, so that both sheets  192  and SS′ are prevented from being bent. Besides, because the diffusion plate DL′ is supported by a surface of the light guide plate  191  via both sheets  192  and SS′, the diffusion plate DL′ is not easily bent. Accordingly, in such backlight unit  182 , a squeak sound caused by bend of both sheets  192 , SS′, and the diffusion plate DL′ is not generated.
     [Patent document 1]: JP-A-2000-10095   

     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     However, in a case of the backlight unit  182  which is shown in  FIG. 27  and three surface views (a plan view, a sectional view taken along the a-a′ line and seen in the a-a′ arrow direction of the plan view, and a sectional view taken along the b-b′ line and seen in the b-b′ arrow direction of the plan view) illustrated in  FIG. 28  and does not incorporate a light guide plate, the diffusion plate DL′ is supported by a frame FM′ that supports the outer edge of the DL′; and the lens sheet SS′ is so located as to cover the diffusion plate DL′. 
     In this case, as shown in  FIG. 29 , the longer sides of the diffusion plate DL′ that are not supported by a surface are easily bent; and further, the lens sheet SS′also is bent together with the bend of the diffusion plate DL′ (the bend tends to occur irregularly and causes deterioration of the quality of backlight). Consequently, contact occurs between the bent diffusion plate DL′ and the like and the frame FM′, so that a squeak sound is generated. 
     The present invention has been made to deal with the conventional situation, and it is an object of the present invention to provide a backlight unit that prevents a squeak sound caused by contact between members from occurring and a liquid crystal display that incorporates the backlight unit. 
     Means for Solving the Problem 
     The present invention is a backlight unit that holds a diffusion member transmitting light from a light source therethrough by supporting the diffusion member with a support frame. In this backlight unit, the diffusion member has a shape the longer and shorter sides of which are able to be defined; and the support frame supports only the shorter sides located at two opposite places of an outer edge of the diffusion member. 
     In such backlight unit, the contact (especially, the contact area) between members that causes a squeak sound has a relatively small area between the shorter sides of the diffusion member and the support frame. Accordingly, it is possible to prevent generation of a squeak sound. 
     As an example of the support frame, there is a support frame that includes: a first block for supporting only two opposite shorter sides of the outer edge of the diffusion member; and a second block facing two opposite longer sides of the outer edge of the diffusion member. It is desirable that the support frame meets the following conditional formula (1) when the thickness of the first block along the thickness direction of the diffusion member is T 1 , and the thickness of the second block along the thickness direction of the diffusion member is T 2 :
 
T 1 &gt;T 2   conditional formula (1)
 
     If the conditional formula (1) is met, the diffusion plate invariably comes into contact with the first block but does not easily come into contact with the second block. Accordingly, the contact between members that causes a squeak sound has a relatively small area. 
     It is desirable that at least one of a support surface, that is, a surface of the first block that supports the diffusion member and an elevation surface, that is, a surface of the second block that faces the diffusion member is concaved. 
     In another backlight unit, the support frame includes: at least three main columns arranged circularly for supporting the diffusion member; and a sub-column that is disposed between the main columns circularly arranged next to each other and shorter than the main columns. 
     Even in such backlight unit, the contact between members that causes a squeak sound has a relatively small area between the diffusion member and the main columns. Accordingly, it is possible to prevent generation of a squeak sound. 
     In a case where a plurality of sub-columns are arranged between the main columns, it is desirable that the lengths of the sub-columns gradually decrease from the main column to the center point between the main columns. According to this arrangement, the bend shape of part of the diffusion plate that corresponds to a region between the main columns can match the shape that virtually connects the tip ends of the sub-columns to each other. Accordingly, the sub-columns have a so suitable shape as to avoid contact with a bent diffusion plate. 
     In a case where the diffusion member has a shape the longer and shorter sides of which are able to be defined, it is desirable that the main column is located to face two opposite shorter sides of the outer edge of the diffusion member; and the sub-column is located to face two opposite longer sides of the outer edge of the diffusion member. A reason for this is that because the longer side of the diffusion plate is prone to be bent compared with the shorter side, it is easy to avoid contact between members if the sub-column is so located as to correspond to the longer side. 
     It is desirable that the support frame includes a third block that faces the two opposite shorter sides of the outer edge of the diffusion member; and the main column is disposed on one surface of the third block that faces the diffusion member. Further, it is desirable that besides the third block, the support frame includes a fourth block that faces the two longer sides of the outer edge of the diffusion member; and the sub-column is disposed on one surface of the fourth block that faces the diffusion member. 
     An end surface of the sub-column that faces the diffusion member may be concaved. Besides, in the backlight unit that includes the third and fourth blocks as the support frame, it is desirable that the following conditional formula (2) is met when the thickness of the third block along the thickness direction of the diffusion member is T 3 , and the thickness of the fourth block along the thickness direction of the diffusion member is T 4 :
 
T 3 &gt;T 4   conditional formula (2)
 
     It is desirable that at least one of the one surface of the third block on which the main column is disposed and the one surface of the fourth block on which the sub-column is disposed is concaved. 
     In the backlight unit described above, the support frame that supports only the shorter sides located at two opposite places of the outer edge of the diffusion member is used as an example. However, the support frame is not limited to this example. For example, the support frame may support only the longer sides located at two opposite places of the outer edge of the diffusion member. 
     A reason for this is that the total contact area between the longer sides located at two opposite places of the outer edge of the diffusion member and the support frame is smaller than the total contact area between both longer and shorter sides of the outer edge of the diffusion member and the support frame; so that it is possible to prevent generation of a squeak sound. 
     There are various kinds of diffusion members. For example, as the diffusion member, there is a diffusion plate for diffusing light from the light source or a diffusion unit that includes a lenticular lens layer disposed on the diffusion plate via an optical member containing dispersed particles. 
     It is desirable that the diffusion member contains methyl methacrylate-styrene or polycarbonate. 
     A liquid crystal display that includes the above backlight unit and a liquid crystal display panel that receives light from the backlight unit is also the present invention. 
     Advantages of the Invention 
     In the backlight unit according to the present invention, the contact area between the inside members becomes extremely small. Accordingly, a squeak sound depending on the contact area is not easily generated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded perspective view of a backlight unit (an example  1 ) shown in  FIG. 25 . 
         FIG. 2  is a three-surface view of  FIG. 1  and shows a plan view, a sectional view taken along the A 1 -A 1 ′ line and seen in the A 1 -A 1 ′ arrow direction, and a sectional view taken along the B 1 -B 1 ′ line and seen in the B 1 -B 1 ′ arrow direction. 
         FIG. 3  is a sectional view taken along the A 1 -A 1 ′ line and seen in the A 1 -A 1 ′ arrow direction in a case where a diffusion plate of the backlight unit is bent. 
         FIG. 4  is an exploded perspective view of another example (an example 2) of the backlight unit shown in  FIG. 1 . 
         FIG. 5  is a three-surface view of  FIG. 4  and shows a plan view, a sectional view taken along the A 2 -A 2 ′ line and seen in the A 2 -A 2 ′ arrow direction, and a sectional view taken along the B 2 -B 2 ′ line and seen in the B 2 -B 2 ′ arrow direction. 
         FIG. 6  is a sectional view taken along the A 2 -A 2 ′ line and seen in the A 2 -A 2 ′ arrow direction in a case where a diffusion plate of the backlight unit is bent. 
         FIG. 7  is an exploded perspective view of another example (an example  3 ) of the backlight units shown in  FIGS. 1 and 4 . 
         FIG. 8  is a three-surface view of  FIG. 7  and shows a plan view, a sectional view taken along the A 3 -A 3 ′ line and seen in the A 3 -A 3 ′ arrow direction, and a sectional view taken along the B 3 -B 3 ′ line and seen in the B 3 -B 3 ′ arrow direction. 
         FIG. 9  is a sectional view taken along the A 3 -A 3 ′ line and seen in the A 3 -A 3 ′ arrow direction in a case where a diffusion plate of the backlight unit is bent. 
         FIG. 10  is an exploded perspective view of another example (an example  4 ) of the backlight units shown in  FIGS. 1 ,  4  and  7 . 
         FIG. 11  is a three-surface view of  FIG. 10  and shows a plan view, a sectional view taken along the A 4 -A 4 ′ line and seen in the A 4 -A 4 ′ arrow direction, and a sectional view taken along the B 4 -B 4 ′ line and seen in the B 4 -B 4 ′ arrow direction. 
         FIG. 12  is a sectional view taken along the A 4 -A 4 ′ line and seen in the A 4 -A 4 ′ arrow direction in a case where a diffusion plate of the backlight unit is bent. 
         FIG. 13  is an exploded perspective view of another example (an example  5 ) of the backlight units shown in  FIGS. 1 ,  4 ,  7  and  10 . 
         FIG. 14  is a three-surface view of  FIG. 13  and shows a plan view, a sectional view taken along the A 5 -A 5 ′ line and seen in the A 5 -A 5 ′ arrow direction, and a sectional view taken along the B 5 -B 5 ′ line and seen in the B 5 -B 5 ′ arrow direction. 
         FIG. 15  is a sectional view taken along the A 5 -A 5 ′ line and seen in the A 5 -A 5 ′ arrow direction in a case where a diffusion plate of the backlight unit is bent. 
         FIG. 16  is an exploded perspective view of another example (an example  6 ) of the backlight units shown in  FIGS. 1 ,  4 ,  7 ,  10  and  13 . 
         FIG. 17  is a three-surface view of  FIG. 16  and shows a plan view, a sectional view taken along the A 6 -A 6 ′ line and seen in the A 6 -A 6 ′ arrow direction, and a sectional view taken along the B 6 -B 6 ′ line and seen in the B 6 -B 6 ′ arrow direction. 
         FIG. 18  is a sectional view taken along the A 6 -A 6 ′ line and seen in the A 6 -A 6 ′ arrow direction in a case where a diffusion plate of the backlight unit is bent. 
         FIG. 19A  is another example of the sectional view taken along the A 6 -A 6 ′ line and seen in the A 6 -A 6 ′ arrow direction of the backlight unit shown in  FIG. 17  that includes different sub-columns. 
         FIG. 19B  is another example of the sectional view taken along the A 6 -A 6 ′ line and seen in the A 6 -A 6 ′ arrow direction of the backlight unit shown in  FIG. 17  that includes a fourth block which has a different thickness. 
         FIG. 19C  is another example of the sectional view taken along the A 6 -A 6 ′ line and seen in the A 6 -A 6 ′ arrow direction of the backlight unit shown in  FIG. 17  that includes a fourth block which has a different shape. 
         FIG. 20  is a sectional view showing a diffusion unit. 
         FIG. 21  is an enlarged sectional view of  FIG. 20 . 
         FIG. 22  is an enlarged sectional view of a region as shown in  FIG. 3 . 
         FIG. 23  is an exploded perspective view of another example of a liquid crystal display shown in  FIG. 25 . 
         FIG. 24  is an enlarged view showing a rib on a first block. 
         FIG. 25  is an exploded perspective view of a liquid crystal display. 
         FIG. 26  is a sectional view showing a conventional backlight unit. 
         FIG. 27  is an exploded perspective view showing a conventional backlight unit. 
         FIG. 28  is a three-surface view of  FIG. 27  and shows a plan view, a sectional view taken along the a-a′ line and seen in the a-a′ arrow direction, and a sectional view taken along the b-b′ line and seen in the b-b′ arrow direction. 
         FIG. 29  is a sectional view taken along the a-a′ line and seen in the a-a′ arrow direction in a case where a diffusion plate of the backlight unit is bent. 
     
    
    
     LIST OF REFERENCE SYMBOLS 
     
         
         
           
             FM support frame 
             SF side holder (support frame) 
             BK block (support frame) 
             BK 1  first block (support frame) 
               1 S one surface of the first block (support surface) 
             BK 2  second block (support frame) 
               2 S one surface of the second block (elevation surface) 
             BK 3  third block (support frame) 
               3 S one surface of the third block 
             BK 4  fourth block (support frame) 
               4 S one surface of the fourth block 
             PE column (support frame) 
             MPE main column (support frame) 
             SPE sub-column (support frame) 
               1 P end surface of main column 
               2 P end surface (opposite end surface) of sub-column 
             DL diffusion plate (diffusion member) 
             Ss lens sheet 
             OD optical member 
             LL lenticular lens layer 
             DLU diffusion unit (diffusion member) 
               21  rib 
               81  liquid crystal display panel unit 
               82  backlight unit 
               83  bezel 
               89  liquid crystal display 
           
         
       
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiment 1 
     An embodiment is explained based on drawings as follows. Member numbers are omitted in some drawings for convenience. In such case, other drawings are referred to. Besides, a black dot in a drawing means a direction perpendicular to the paper surface. 
       FIG. 25  shows an exploded perspective view of a liquid crystal display  89 . As shown in  FIG. 25 , the liquid crystal display  89  includes a liquid crystal display panel unit  81 , a backlight unit  82 , and a bezel  83  that covers the outer edges of both units  81  and  82 . 
     The liquid crystal display panel unit  81  includes a liquid crystal display panel  61  and a frame-shaped chassis (panel chassis)  62  that supports the outer edge of the liquid crystal display panel  61 . 
     The liquid crystal display panel  61  includes a active matrix board (AM board)  63 , an opposite board  64  that is opposite and bonded to the AM board  63  with a sealant (not shown), and liquid crystal (not shown) injected into the gap between the two boards  63  and  64 . The liquid crystal display panel  61  includes an optical member (e.g., a polarization sheet, a phase retardation sheet: not shown) that sandwiches the AM board  63  and the opposite board  64 . 
     The liquid crystal display panel  61  is supported by the panel chassis  62  and is located so as to overlay the backlight unit  82 , and functions as a display panel that receives light (backlight) from the backlight unit  82 . 
     The backlight unit  82  includes a fluorescent lamp (light source)  71 , a side holder SF (support frame FM), a reflection sheet  72 , a diffusion plate (diffusion member) DL, a lens sheet SS, a backlight chassis  73 , and a support pin base  74 . 
     The fluorescent lamp (linear light)  71  emits light and a plurality of the fluorescent lamps  71  are arranged in the backlight unit  82  (only a few of them are shown in the figure for convenience). Here, the length in the direction (arrangement direction) in which the fluorescent lamps  71  are arranged is shorter than the length in the longitudinal direction of the fluorescent lamp  71 . Accordingly, if a surface is defined by the plurality of fluorescent lamps  71  arranged, the surface becomes rectangular. From this reason, hereinafter, the arrangement of the fluorescent lamps  71  is called a rectangular arrangement. Besides, hereinafter, the arrangement direction of the fluorescent lamps  71  is called a first direction D 1  and the linear direction (longitudinal direction) of the fluorescent lamp  71  is called a second direction D 2 . 
     The side holder SF includes: a block BK (a first block BK 1 ; see  FIG. 1 ) that supports one end of the plurality of fluorescent lamps  71 ; and a block BK (the first block BK 1 ) that supports the other end of the plurality of fluorescent lamps  71 . In other words, the side holder SF holds the fluorescent lamps  71  by supporting both ends of the plurality of fluorescent lamps  71 . 
     The first block BK servings as the side holder SF has a plate shape, and one surface (support surface  1 S) of the first block BK in the same direction as that in the surface of a bottom portion  73   a  of the backlight chassis  73  (in detail, the reflection sheet  72  located on the bottom portion  73   a  of the backlight chassis  73 ) faces the diffusion plate DL. 
     The reflection sheet  72  is so located as to be covered by the rectangularly arranged fluorescent lamps  71 , so that the reflection sheet  72  reflects part of the radial light (the radial light with respect to the fluorescent lamps  71 ) emitted from the fluorescent lamps  71 . 
     The diffusion plate DL is formed of a resin such as methyl methacylate-styrene or polycarbonate that have a function to disperse light and a function to diffuse light, and is so located as to cover the rectangularly arranged fluorescent lamps  71 . Accordingly, the diffusion plate DL receives the light (emitted light) from the fluorescent lamps  71  and the light (reflected light) from the reflection sheet  72 , disperses and diffuses them so as to spread the light in the surface direction. 
     The diffusion plate DL is easily deformed (easily bent) by heat. However, in the production process, it is possible to predict a bend direction of the diffusion plate DL according to a difference between machining temperatures respectively applied to the front surface and the back surface of the diffusion plate DL. Especially, in a case where the diffusion plate DL has a rectangular shape so as to cover the rectangularly arranged fluorescent lamps  71 , because the diffusion plate DL is easily bent in the longitudinal direction, it is easy to predict the bend direction. 
     For example, the lens sheet SS has a lens shape in the sheet surface, deflects (collects light) the radiation characteristic of light and is so located as to cover the diffusion plate DL. Accordingly, the lens sheet SS receives light going through the diffusion plate DL and collects the light so as to improve the light brightness per area. 
     The backlight chassis  73  is a chassis that is able to house the fluorescent lamps  71 , the reflection sheet  72 , the diffusion plate DL, the lens sheet SS and the like. However, the shape is not limited. For example, as shown in  FIG. 25 , a box-shaped backlight chassis  73  may be employed. 
     The support pin base  74  is so formed as to be upright from the bottom portion  73   a  of the backlight chassis  73 . The support pin base  74  protrudes a support pin  74   a  through an opening formed through a portion of the reflection sheet  72  and further through between the fluorescent lamps  71 ,  71 . Accordingly, the support pin base  74  supports the diffusion plate DL by making the support pin  74   a  come into contact with the diffusion plate DL that is so located as to cover the fluorescent lamps  71 . The length of the support pin  74   a  is not limited. 
     Besides, the support pin base  74  includes fluorescent lamp hooks  74   b ,  74   b  for grasping the fluorescent lamp  71  on both sides of the bottom end of the support pin  74   a . Accordingly, the support pin  74  supports the diffusion plate DL with the support pin  74   a  and surely fixes the fluorescent lamp  71  with the fluorescent lamp hooks  74   b.    
     Here, the backlight unit  82  is described in detail using the simplified  FIGS. 1 to 3  (the example  1 ) of the backlight unit  82  shown in  FIG. 25 .  FIG. 1  is an exploded perspective view of the backlight unit  82 ;  FIG. 2  is a three-surface view (a plan view of the backlight unit  82 , a sectional view taken along the A 1 -A 1 ′ line and seen in the A 1 -A 1 ′ arrow direction in the plan view, and a sectional view taken along the B 1 -B 1 ′ line and seen in the B 1 -B 1 ′ arrow direction in the plan view); and  FIG. 3  is a sectional view taken along the A 1 -A 1 ′ line and seen in the A 1 -A 1 ′ arrow direction in a case where the diffusion plate DL of the backlight unit  82  is bent. In these figures, the support pin base  74  is omitted for convenience. 
     As shown in  FIGS. 1 to 3 , the backlight unit  82  supports the diffusion plate DL for transmitting the light from the fluorescent lamps  71  with the support surfaces  1 S,  1 S that are each one surface of the side holder SF (in detail, the first blocks BK 1 , BK 1 ) and thus holds the diffusion plate DL. Accordingly, the side holder SF is also called a support frame FM. Especially, the support frame FM that plays a role of the side holder SF as well supports only shorter sides located at two opposite places (two opposite shorter sides) of the outer edge of the diffusion plate DL that has a shape, for example, a rectangular shape which is able to be defined by longer and shorter sides. 
     Besides, the backlight unit  82  matches a predictable bend direction of the diffusion plate DL (in detail, a bend direction of the longer sides of the diffusion plate DL) with a direction that goes away from the liquid crystal display panel  61 . Accordingly, if light heat from the fluorescent lamps  71  acts on the diffusion plate DL, the diffusion plate DL is bent (curved) toward the reflection sheet  72  as shown by the white arrows in  FIG. 3 . 
     Here, in this backlight unit  82 , only the shorter sides of the outer edge of the diffusion plate DL come in contact with the support frame FM. Accordingly, even if the longer sides of the outer edge of the diffusion plate DL are bent, the longer sides do not come into contact with any members, so that an unusual sound (a squeak sound) caused by contact is not generated. Besides, even if the diffusion plate DL returns to the original state when the heat acting on the diffusion plate DL is radiated after the fluorescent lamps  71  are turned off, the longer sides of the diffusion plate DL do not come into contact with any members, so that a squeak sound caused by contact is not generated. 
     In other words, the backlight unit  82  makes the contact area as small as possible between the diffusion plate DL and the support frame FM (in other words, only the shorter sides of the diffusion plate DL come into contact with the support frame FM), thereby lowering a squeak sound caused by the contact between both diffusion plate DL and support frame FM. 
     From the viewpoint for the smallest possible contact area between the diffusion plate DL and the support frame FM, the support frame FM may support longer sides located at two opposite places (two opposite longer sides) of the outer edge of the diffusion plate DL. A reason for this is that the contact area between only the two opposite longer sides of the outer edge of the diffusion plate DL and the support frame FM is smaller than the contact area between both longer and shorter sides of the outer edge of the diffusion plate DL and the support frame FM; accordingly, it is possible to prevent a squeak sound from being generated. 
     There are some other examples of the above backlight unit  82  that relatively reduces the contact area between the diffusion plate DL and the support frame FM. For example, there are a backlight unit  82  according to an example  2  shown in  FIGS. 4 to 6 , and a backlight unit  82  according to an example  3  shown in  FIGS. 7 to 9 .  FIGS. 4 and 7  are illustrated in the same way as  FIG. 1 ,  FIGS. 5 and 8  are illustrated in the same way as  FIG. 2 , and  FIGS. 6 and 9  are illustrated in the same way as  FIG. 3 . 
     In the backlight unit  82  according to the example  2 , two blocks BK (second blocks BK 2 , BK 2 ) each having one surface (elevation surface  2 S) in the same direction as that of the support surface  1 S of the block BK 1 , that is, the support frame FM, are included. Hereinafter, an explanation is performed describing that these second blocks BK 2  are part of the support frame FM. 
     The backlight unit  82  in the example  2  includes, as the support frame FM, the first blocks BK 1 , BK 1  that support only the two opposite shorter sides of the outer edge of the diffusion plate DL and the second blocks BK 2 , BK 2  that face the two opposite longer sides of the outer edge of the diffusion plate DL. 
     The thickness of the first block BK 1  along the plate-thickness direction (thickness direction) of the diffusion plate DL is different from the thickness of the second block BK 2  along the plate-thickness direction (thickness direction) of the diffusion plate DL. Specifically, when the thickness of the first block BK 1  is T 1  and the thickness of the second block BK 2  is T 2 , the following conditional formula A is met (see  FIG. 5 ):
 
T 1 &gt;T 2   conditional formula A
 
     According to this, as shown in  FIG. 6 , even if the longer sides of the diffusion plate DL are bent, the longer sides and the second block BK 2  do not come into contact with each other, so that a squeak sound caused by contact is not generated. Specifically, the backlight unit  82  provides a space for accepting a bend (warp) of the diffusion plate DL between the diffusion plate DL and the second block BK 2  by meeting the conditional formula A [conditional formula (1)]. 
     In the backlight unit  82  according to the example  3  shown in  FIGS. 7 to 9 , the elevation surface  2 S, that is, one surface of the second block BK 2  that faces the diffusion plate DL is concaved. In detail, the second block BK 2  is concaved deepest at the center of the longer side thereof and the concave amount decreases from the center to the end of the longer side so that the elevation surface  2 S is concaved into a curved surface. 
     Because of this concaved surface, as shown in  FIG. 9 , even if the longer sides of the diffusion plate DL are bent, the longer sides and the elevation surface  2 S of the second block BK 2  do not come into contact with each other, so that a squeak sound caused by contact is not generated. Specifically, in the backlight unit  82 , a space for accepting a bend of the diffusion plate DL is provided between the diffusion plate DL and the elevation surface  2 S of the second block BK 2  by concaving the elevation surface  2 S. 
     The concave is not limited only to the elevation surface  2 S of the second block BK 2 , and may be formed on the support surface  1 S, that is, one surface of the first block BK 1  that supports the diffusion plate DL (The support surface  1 S may be concaved into a curved surface with the first block BK 1  concaved deepest at the center of the longer side thereof and the concave amount decreases from the center to the end of the longer side). 
     This is because a bend is formed on the shorter side of the diffusion plate DL as well. Specifically, according to this, the contact area between the shorter side of the diffusion plate DL and the support surface  1 S of the first block BK 1  becomes relatively small, so that a squeak sound depending on the contact area becomes low. 
     Accordingly, if both of the elevation surface  2 S of the second block BK 2  and the support surface  1 S of the first block BK 1  are concaved, it is possible to prevent a squeak sound from being generated most effectively. However, even if at least one of the support surface  1 S of the first block BK 1  and the elevation surface  2 S of the second block BK 2  is concaved, the effect of reducing a squeak sound is obtained. 
     Besides, the second blocks BK 2 , BK 2  are located between the first blocks BK 1 , BK 1  of the support frame FM (between one end of one of the first opposite blocks BK 1  and one end of the other of the first opposite blocks BK 1 ), thereby preventing foreign matter from invading the backlight unit  82 . Accordingly, it is desirable that the adjacent first blocks Bk 1 , BK 1  and the second blocks BK 2 , BK 2  are in tight contact with each other (they may be connected to each other). 
     In addition, the second block BK 2  prevents the diffusion plate DL from being excessively bent toward the reflection sheet  72  (the bottom portion of the backlight chassis  73 ). Specifically, only if the diffusion plate DL is excessively bent, the second blocks BK 2  play a role in supporting the diffusion plate DL. 
     Embodiment 2 
     An embodiment 2 is explained. Here, members that have the same functions as those used in the embodiment 1 are indicated by the same reference numbers and the explanation of them is skipped. 
     As one of the causes of a squeak sound in the backlight unit  82 , there is contact between the diffusion plate DL and other members (the side holder SF and the like). Accordingly, the backlight unit  82  that does not easily generate such contact is desirable for reduction in a squeak sound. From this reason, hereinafter, an example (examples  4  to  6 ) of such backlight unit  82  is explained. 
       FIGS. 10 to 12 ,  13  to  15 , and  16  to  18  show backlight units  82  in the examples  4  to  6 , respectively.  FIGS. 10 ,  13  and  16  are illustrated in the same way as  FIG. 1 ,  FIGS. 11 ,  14  and  17  are illustrated in the same way as  FIG. 2 , and  FIGS. 12 ,  15  and  18  are illustrated in the same way as  FIG. 3 . 
     In the backlight unit  82  according to the example  4  shown in  FIGS. 10 to 12 , the fluorescent lamps  71  is supported by only the support pin base  74  (see  FIG. 25 ), not shown. In other words, in the backlight unit  82  according to the example  4 , a side holder for holding both ends of the fluorescent lamp  71  is not incorporated. Accordingly, in this backlight unit  82 , the diffusion plate DL is supported by columns PE circularly arranged in a plane (Accordingly, the column PE is able to be called the support frame FM). In detail, the columns PE include two kinds of components, that is, a main column MPE and a sub-column SPE. 
     The main column MPE is a column that supports the diffusion plate DL by always making one surface  1 P which has a smaller area than the support surface  1 S of the first block BK 1  come in contact with the diffusion plate DL, and is so formed as to be upright from the backlight chassis  73  (in detail, from the reflection sheet  72  located on the bottom portion  73   a  of the backlight chassis  73 ). Accordingly, the contact area between the main column MPE and the diffusion plate DL becomes smaller than the contact area between the first block BK 1  and the diffusion plate DL, thereby curbing generation of a squeak sound. 
     In the backlight unit  82  according to the example  4 , although the main columns MPE come into contact with the four corners (both ends of each of the shorter sides of the diffusion plate DL) of the rectangular diffusion plate DL, this is not limitation. Because the main columns MPE support the diffusion plate DL by coming into contact with the diffusion plate DL, it is desirable that more main columns MPE are used. However, it can also be said that at least three main columns MPE need only to be arranged circularly so as to stably support a surface-shaped member like the diffusion plate DL. 
     The sub-columns SPE is a column that does not come into contact with the diffusion plate DL. However, the sub-column SPE prevents the diffusion plate DL from being excessively bent toward the reflection sheet  72 . In other words, the sub-column SPE is the column PE that supports the diffusion plate DL only if the diffusion plate DL is excessively bent. For this purpose, the sub-column SPE is shorter than the main column MPE (the length T S  of the sub-column SPE&lt;the length T M  of the main column MPE; conditional formula B), so that the sub-columns SPE do not come into contact with the diffusion plate DL that is bent in an expected range. Like the main column MPE, the sub-column SPE is so formed as to be upright from the backlight chassis  73 . 
     A bend of the diffusion plate DL is generated by deformation of other places with respect to the place supported by the main column MPE (In other words, places that are nor supported by the main column MPE are easily bent). Accordingly, it is desirable that the sub-columns SPE are located between the adjacent main columns MPE, MPE as in the backlight unit  82  according to the example  4 . In other words, the sub-columns SPE need only to be located between the circularly adjacent main columns MPE, MPE. 
     If the diffusion plate DL is bent with respect to the place where the diffusion plate DL is supported by the main column MPE, usually the bend amount of the diffusion plate DL corresponding to the central portion between the main columns MPE, MPE becomes largest, and gradually decreases from the central portion to the main column MPE (Here, the bend amount is a change amount in the position of the diffusion plate DL before and after a bend.) 
     Accordingly, it is desirable that the length of the sub-column SPE gradually decreases from the main column MPE to the center point between the main columns MPE, MPE. From this reason, for example, in the backlight unit  82  according to the example  4 , the length T S  of the sub-column SPE corresponding to the central portion between the main columns MPE, MPE along the longer side of the diffusion plate DL is made shorter than the lengths T S  of the sub-columns SPE located from the place near the central portion between the main columns MPE, MPE to the main column MPE. 
     Accordingly, both of the part of the diffusion plate DL that corresponds to the central portion between the main columns MPE, MPE and has a relatively large bend amount and the part of the diffusion plate DL that corresponds to the place near the main column MPE and has a relatively small bend amount do not come into contact with the sub-columns SPE. Besides, it becomes hard for foreign matter to invade from between the main columns MPE, MPE. 
     As described above, as an example of the case where the part of the diffusion plate DL corresponding to the center portion between the main columns MPE, MPE is easily bent, there is a case where in the diffusion plate DL that has a shape (e.g., a rectangular shape) the longer and shorter sides of which are able to be defined, the main columns MPE are located corresponding to the two opposite shorter sides of the outer edge of the diffusion plate DL. Accordingly, in such a case, it is desirable that the sub-columns SPE are located corresponding to the two opposite longer sides of the outer edge of the diffusion plate DL. 
     In the meanwhile, in the backlight unit  82  according to the embodiment 4, the fluorescent lamp  71  is supported by only the support pin base  74  (see  FIG. 25 ). If it is desired to support the fluorescent lamp  71  more stably than in such backlight unit  82 , a backlight unit such as the backlight unit  82  in the embodiment 5 is able to be used. 
     In the backlight unit  82  according to the example  5  shown in  FIGS. 13 to 15 , third blocks BK 3 , BK 3  that play the role of the side holder SF are located at both ends of the fluorescent lamps  71 . Accordingly, the third blocks BK 3  are so located as to face the two opposite shorter sides of the outer edge of the diffusion plate DL. Besides, in this backlight unit  82 , the main columns MPE are so disposed as to be upright on one surface (one surface  3 S that faces the diffusion plate DL) of the third block BK 3 . 
     In other words, the backlight unit  82  according to the example  5  incorporates a unitary component of the third block BK 3  and the main columns MPE, and the sub-columns SPE as the support frame FM. Accordingly, the support frame FM stably holds the fluorescent lamps  71  with the third blocks BK 3 , while the diffusion plate DL also is able to be supported by the main columns MPE. 
     In the backlight unit  82  according to the example  6  shown in  FIGS. 16 to 18 , blocks BK (fourth blocks BK 4 ) that face the two opposite longer sides of the outer edge of the diffusion plate DL are disposed, and the sub-columns SPE are so disposed as to be upright on one surface (one surface  4 S that faces the diffusion plate DL) of the fourth block BK 4 . In other words, the backlight unit  82  according to the example  6  incorporates, as the support frame FM, a unitary component of the third block BK 3  and the main columns MPE and a unitary component of the fourth blocks BK 4  and the sub-columns SPE. 
     Accordingly, the support frame FM stably holds the fluorescent lamps  71  with the third blocks BK 3 , supports the diffusion plate DL with the main columns MPE, and further, prevents foreign matter from invading through between the third blocks BK 3 , BK 3  (between one end of one of the third opposite blocks BK 3  and one end of the other of the third opposite blocks BK 3 ) with the sub-columns SPE and the fourth blocks BK 4 . 
     Here, the sub-columns SPE disposed on the fourth blocks BK 4  have lengths so as not to come into contact with the diffusion plate DL that is bent in an expected range. Besides, as described above, it is desirable that the length T S  of the sub-column SPE corresponding to the central portion between the main columns MPE, MPE along the longer side of the diffusion plate DL is made shorter than the lengths T S  of the sub-columns SPE located from the place near the central portion between the main columns MPE, MPE to the main column MPE (see  FIG. 17 ). 
     As shown in  FIG. 19A , one surface (an opposite end surface  2 P; see  FIG. 17 ) of the sub-column SPE that faces the diffusion plate DL may be so concaved as not to come into contact with the diffusion plate DL. Besides, it is desirable that a thickness relationship between the third block BK 3  corresponding to the shorter side of the diffusion plate DL and the fourth block BK 4  corresponding to the longer side of the diffusion plate DL meets the following conditional formula C [the conditional formula (2)] (see  FIG. 19B ):
 
T 3 &gt;T 4   conditional formula C
 
where
 
     T 3 : thickness of the third block BK 3  along the thickness direction of the diffusion plate DL 
     T 4 : thickness of the fourth block BK 4  along the thickness direction of the diffusion plate DL 
     The thickness T 3  of the third block BK 3  must have a constant thickness so as to hold the fluorescent lamps  71 . On the other hand, because the fourth block BK 4  does not hold the fluorescent lamps  71 , the degree of freedom of the thickness T 4  of the fourth block Bk 4  is high. Accordingly, from the viewpoint of cost reduction, it is desirable that the thickness T 4  of the fourth block BK 4  is thinner than the thickness T 3  of the third block BK 3 . 
     As shown in  FIG. 19C , the one surface  4 S of the fourth block BK 4  on which the sub-columns SPE are disposed may be concaved. In detail, the fourth block BK 4  is concaved deepest at the center of the longer side thereof and the concave amount decreases from the center to the end of the longer side, so that the one surface  4 S of the fourth block BK may be concaved into a curved surface. 
     Accordingly, even when the sub-columns SPE have the same length, if the sub-columns SPE are spaced apart from each other on the concaved surface  4 S of the fourth block BK 4 , the distances from the tip ends (the opposite end surfaces  2 P) of the sub-columns SPE to the bottom portion of the fourth block BK 4  change. 
     In other words, at the sub-column SPE located at the most deeply concaved center portion of the longer side of the fourth block BK 4  and at the sub-columns SPE located at the other positions of the longer side of the fourth block BK 4 , the distances from the tip ends of the sub-columns SPE to the bottom of the fourth block BK 4  change. Accordingly, the backlight unit  82  is able to achieve the arrangement of the sub-columns SPE with the same-length sub-columns SPE considering the bend amount of the diffusion plate DL. 
     The concave portion may be formed not only on the one surface  4 S of the fourth block BK 4  but also on the one surface  3 S of the third block BK 3  on which the main columns MPE are located (the third block BK 3  is concaved deepest at the center of the longer side thereof and the concave amount decreases from the center to the end of the longer side, so that the one surface  3 S may be concaved into a curved surface). 
     According to the concaved surface, even when the main columns MPE have the same length, if the main columns MPE are spaced apart from each other on the concaved surface  3 S of the third block BK 3 , the distances from the tip ends of the main columns MPE to the bottom portion of the third block BK 3  change. Because of this, the backlight unit  82  is able to relatively reduce the contact area between the shorter sides of the diffusion plate DL and the main columns MPE and lower a squeak sound that depends on the contact area by disposing some of the plurality of main columns MPE so as to be away from the diffusion plate DL. 
     Accordingly, if both of the one surface  4 S of the fourth block BK 4  and the one surface  3 S of the third block BK 3  are concaved, it is possible to prevent a squeak sound from being generated most effectively. However, even if at least one of the one surface  3 S of the third block BK 3  and the one surface  4 S of the fourth block BK 4  is concaved, the effect of reducing a squeak sound is obtained. 
     Embodiment 3 
     An embodiment 3 is explained. Here, members that have the same functions as those used in the embodiments 1 and 2 are indicated by the same reference numbers and the explanation of them is skipped. 
     In the embodiments 1 and 2, the diffusion plate DL is described as the member (the diffusion member) that has a function to disperse and diffuse light. However, the diffusion member incorporated in the backlight unit  82  is not limited to the diffusion plate DL. 
     For example, a diffusion unit DLU shown in  FIGS. 20 and 21  (an enlarged view of  FIG. 20 ) may be incorporated in the backlight unit  82 . The diffusion unit DLU includes the diffusion plate DL, a lenticular lens layer LL, and an optical member OD. 
     Here, the diffusion unit DLU is described in detail. Like in the embodiments 1 and 2, the diffusion plate DL of the diffusion unit DLU is formed of a resin such as polycarbonate or methyl methacrylate-styrene that have a function to disperse light. 
     On the other hand, the lenticular lens layer LL is formed of polyethylene terephthalate or the like, and includes a surface-shaped supporter  11  and a plurality of cylindrical lenses (lenticular lenses) LS (see  FIG. 21 ). The plurality of cylindrical lenses LS are arranged on the supporter  11  in parallel with each other. The arrangement direction of the cylindrical lenses LS is the same as the first direction D 1  that is the arrangement direction of the fluorescent lamps  71 . Besides, the longitudinal direction of the cylindrical lens LS is the same as the second direction D 2  that is the longitudinal direction of the fluorescent lamp  71 . 
     The optical members OD are arranged in a space (a sandwiched layer  12 ) defined between the diffusion plate DL and the lenticluar lens layer LL that face each other across a gap therebetween. Accordingly, the diffusion plate DL and the lenticular lens layer LL are unitarily bonded to each other with the aid of adhesive force of adhesives attaching to the optical members OD. The optical members OD are each formed into a linear shape (a plate shape or the like) and arranged in parallel to each other via gaps  13  provided in the sandwiched layer  12 . The arrangement direction of the optical members OD is the same as the first direction D 1  that is the arrangement direction of the cylindrical lenses LS. Besides, the linear direction (the longitudinal direction) of the optical members OD is the same as the second direction D 2  that is the longitudinal direction of the cylindrical lenses LS. 
     Here, the optical members OD need only to include at least a chief component and dispersed particles and the materials of the chief component and the particles are not limited. For example, an acrylic resin is used for the chief component, and titanium oxide is used for the dispersed particles. 
     The above diffusion unit DLU is easily deformed (bent) by heat like the diffusion plates DL in the embodiments 1 and 2. Besides, like the diffusion plate DL, the bend direction of the diffusion unit DLU is predictable. In addition, like the diffusion plate DL, the rectangular-shaped diffusion unit DLU is easily bent in the longitudinal direction. 
     Accordingly, it is possible to support the diffusion unit DLU by using the support frames FM described in the embodiments 1 and 2, and the functions and effects described above are also obtained in the backlight unit  82  that incorporates the diffusion unit DLU. Besides, a further effect is also obtained from the difference between the deformation of the lenticular lens layer LL caused by the bend of the diffusion unit DLU and the deformation of the lens sheet SS located on the bent diffusion plate DL in the embodiments 1 and 2. The effect is an improved quality of the backlight. 
     The lens sheet SS located on the bent diffusion plate DL in the embodiments 1 and 2 is bent together with the bend of the diffusion plate DL. However, because the lens sheet SS and the diffusion plate DL are not formed unitarily with each other, the lens sheet SS is bent differently from the diffusion plate DL. For example, as shown in  FIG. 22  that is an enlarged view of the region α in  FIG. 3 , the lens sheet SS has places (β) that are bent without coming into tight contact with the diffusion plate DL. 
     In other words, the way the lens sheet SS is bent is unpredictable and has no regularity. Accordingly, the backlight passing through the lens sheet SS which is bent with no regularity cannot travel in a desired direction and is not high-quality backlight. Also the image quality of the liquid crystal display panel  61  that receives such backlight and functions as a display device does not have a high grade. 
     On the other hand, the lenticular lens layer LL of the diffusion unit DLU is bent together with the bend of the diffusion plate DL of the diffusion unit DLU. However the lenticular lens layer LL and the diffusion plate DL are formed unitarily with each other. Because of the unitary formation, the lenticular lens layer LL is in tight contact with the diffusion plate DL via the optical members OD and is bent like the diffusion plate DL. Accordingly, the way the lenticular lens layer LL is bent is predictable and has regularity. 
     Because the backlight unit  82  incorporates the diffusion unit DLU that includes the lenticular lens sheet SS that is bent with regularity, it is possible to design a structure in which the backlight passing through the bent lenticular lens layer LL travels in a desired direction, thereby supplying high-quality backlight. In other words, besides the functions and effects described in the embodiments 1 and 2, this backlight unit  82  is able to supply high-quality backlight. Consequently, the image quality of the liquid crystal display panel  61  that receives the supplied backlight and functions as the display device reaches a high grade. 
     To sum up, the diffusion unit DLU assumes bend of the lenticular lens layer LL and the diffusion plate DL and has a structure so as not to deteriorate the backlight quality by considering the bend. In other words, the diffusion unit DLU is a member that is allowed to be bent. Accordingly, the backlight unit  82  that incorporates the diffusion unit DLU positively allows the diffusion unit DLU to be bent without considering the backlight quality and avoids contact between the support frame FM and the diffusion unit DLU by using the support frame FM (the support frames FM described in the embodiments 1 and 2) that is variously designed. 
     On the other hand, as in the backlight unit  82  according to the embodiments 1 and 2, in the arrangement relationship in which the lens sheet SS is disposed on the diffusion plate DL, the diffusion plate DL that is not bent is most desirable so as not to allow bend of the lens sheet SS that easily follow bend of the diffusion plate DL. In other words, unlike the diffusion unit DLU, the diffusion plate DL is a member that is not allowed to be bent. 
     However, in a case where the diffusion plate DL is easily bent because of the material, the backlight unit  82  allows bend of the diffusion plate DL in order for the diffusion plate DL to be away from the liquid crystal display panel  61 , thereby avoiding contact between the lens sheet SS on the diffusion plate DL and the liquid crystal display panel  61  and securing the backlight quality more or less. Further, the backlight unit  82  avoids contact between the support frame FM and the diffusion plate DL by using the support frame FM that is variously designed. 
     Accordingly, it is most effective in terms of maintenance of the backlight quality and prevention of a squeak sound that the diffusion unit DLU is incorporated in the backlight unit  82  that prevents a squeak sound from being generated with the support frame FM that is variously designed. 
     Other Embodiments 
     The present invention is not limited to the above embodiments and it is possible to make various modifications without departing from the spirit of the present invention. 
     For example, the fist block BK 1  and the second block BK 2  and the like used as the support frame FM are not limited to the type that is housed in the backlight chassis  73 . As an example, as shown in  FIG. 23 , the backlight unit  82  may be used, which incorporates the backlight chassis  73  that includes the bottom portion  73   a  covered by the reflection sheet  72 , and the wall portions  73   b  upright from the outside edges of the circumference of the bottom portion  73   a  along the longitudinal direction of the fluorescent lamp  71 . A reason for this is that in this backlight unit  82 , for example, only the first block BK 1  is housed in the backlight chassis  73 , while the wall portions  73   b  of the backlight chassis  73  play the role of the second block BK 2 . 
     Besides, the backlight unit  82  that incorporates the reflection sheet  72  is explained as an example. However, this is not limitation, and it may be a backlight unit  82  that does not incorporate the reflection sheet  72 . 
     To reduce the contact area between the diffusion plate DL and the support frame FM, as shown in  FIG. 24  (an enlarged view of  FIG. 25 ), ribs  21  may be arranged on the support surface  1 S of the first block BK 1  and the like. According to this arrangement, the contact area between the ribs  21  and the diffusion plate DL is smaller than the contact area between the first blocks BK 1  and the diffusion plate DL, thereby allowing further reduction in a squeak sound. Here, the ribs  21  may be formed not only on the first blocks BK 1  but also on the one surface (the one surface facing the diffusion plate DL) of the blocks BK 2  to BK 4 . 
     It can be said that the chief roles of the second blocks BK 2  and the sub-columns SPE change depending on the length of the support pin  74   a  of the support pin base  74 . In detail, in a case where the tip end of the support pin  74   a  is closer to the diffusion plate DL than the elevation surfaces  2 S of the second blocks BK 2  and the end surfaces  2 P of the sub-columns SPE, the elevation surfaces  2 S of the second blocks BK 2  and the sub-columns SPE chiefly play a role in preventing foreign matter from invading inside the backlight unit  82 . On the other hand, in a case where the tip end of the support pin  74   a  is more away from the diffusion plate DL than the elevation surfaces  2 S of the second blocks BK 2  and the end surfaces  2 P of the sub-columns SPE, the elevation surfaces  2 S of the second blocks BK 2  and the sub-columns SPE chiefly play a role in supporting the diffusion plate DL or the diffusion unit DLU.