Patent Publication Number: US-2015077643-A1

Title: Lighting device, display device, and television device

Description:
TECHNICAL FIELD 
     The present invention relates to a lighting device, a display device, and a television device. 
     BACKGROUND ART 
     In recent years, displays in image display devices, such as television devices, are being shifted from conventional cathode-ray tube displays to thin displays, such as liquid crystal displays and plasma displays. With the thin displays, thicknesses of the image display devices can be decreased. Liquid crystal panels do not emit light. Therefore, liquid crystal display devices including liquid crystal panels require backlight devices. The backlight devices are classified broadly into a direct type and an edge-light type based on mechanisms. For further reduction in thicknesses of the liquid crystal display devices, the edge-light type backlight devices are more preferable. A backlight devices disclosed in Patent Document 1 is known as an example of the kind. 
     RELATED ART DOCUMENT 
     Patent Document 
     Patent Document 1: Japanese Unexamined Patent Publication No. 2011-232607 
     Problem to be Solved by the Invention 
     In the above edge-light backlight unit, because light sources are arranged locally in an end portion of a chassis included in the backlight unit, it may be difficult to allocate a space for attaching the light sources to the chassis. Specifically, if LEDs are used as the light sources, a screw is necessarily arranged between adjacent LEDs to attach an LED board including the LEDs to the chassis. Therefore, an interval between the adjacent LEDs with the screw therebetween is relatively larger than intervals between other LEDs, and thus an amount of light entering a light guide plate is partially small in some areas. The areas may be recognized as dark portions. 
     DISCLOSURE OF THE PRESENT INVENTION 
     The present invention was made in view of the above reasons and an object of this invention is to reduce uneven brightness. 
     Means for Solving the Problem 
     A lighting device according to this invention includes a plurality of light sources, a light guide plate, a light source board, a mount member, a board attachment member, and a plurality of arrangement interval variation light sources. The light guide plate includes an end surface and a plate surface. The end surface is opposite the light sources. Light from the light sources enters the light guide plate through the end surface and exits the light guide plate through the plate surface. The light source board is provided with the light sources that are arranged at intervals along the end surface of the light guide plate. The mount member is provided with the light source board mounted thereon. The board attachment member is arranged between the light sources adjacent to each other and attaches the light source board to the mount member. The plurality of arrangement interval variation light sources are included in the light sources and arranged such that the intervals between the arrangement interval variation light sources decrease as a distance from the board attachment member increases. 
     In this configuration, light emitted from the light sources enters the light guide plate through the end surface and travel within the light guide plate and then exits the light guide plate  19  through the plate surface. The light source board includes the light sources mounted thereto such that the light sources are arranged at intervals along the end surface of the light guide plate. The board attachment member to attach the light source board to the mount member is disposed between the light sources that are adjacent to each other. The interval between the adjacent light sources with board attachment member therebetween tends to be large because a space needs to be provided to arrange the board attachment member. Accordingly, the amount of light entering through the end surface of the light guide plate may be partially small, and this may cause a dark portion. However, as is described above, the light sources include the arrangement interval variation light sources that are arranged such that the intervals therebetween decrease as the distance from the board attachment member increases. Therefore, the amount of light emitted from at least the arrangement interval variation light sources to the end surface of the light guide plate per unit area gradually varies according to the distance from the board attachment member. Accordingly, a dark portion is less likely to be caused at the end surface of the light guide plate, and thus uneven brightness is less likely to occur in the exiting light. 
     The following configurations are preferable as aspects of this invention. 
     (1) The arrangement interval variation light sources may include at least a pair of first light sources, a second light source, and a third light source. The pair of first light sources may be arranged with having the board attachment member therebetween. The second light source may be arranged adjacent to at least one of the first light sources such that an interval between the at least one of first light sources and the second light source is smaller than an interval between the pair of first light sources. The third light source may be arranged adjacent to the second light source such that an interval between the second light source and the third light source is smaller than the interval between the at least one of the first light sources and the second light source. In the above configuration, the interval gradually decreases in the following sequence: the interval provided between the first light sources that are arranged with the board attachment member in between, the interval provided between the one of the first light sources and the second light source adjacent to the first light sources, and the interval provided between the second light source and the third light source adjacent to the second light sources. Accordingly, the amount of light entering through the end surface of the light guide plate  19  gradually varies according to the distance from the board attachment member, and thus a dark portion is less likely to occur. 
     (2) The light reflection portions are configured to reflect light in the light guide plate toward a light exiting side to increase light exiting from the plate surface of the light guide plate and may be arranged such that an area distribution of the light reflection portions in a plane of the plate surface of the light guide plate decreases along an arrangement direction of the light sources as the distance from the board attachment member increases. In the above configuration, the light reflection portions that are configured to reflect light in the light guide plate toward the light exit side are arranged such that the area distribution thereof in the plane of the plate surface of the light guide plate decreases as the distance from the board attachment member along the arrangement direction of the light sources increases. Therefore, light from the light sources that are arranged at the relatively large interval is more likely to be reflected by the light reflection portions, and light from the light sources arranged at the relatively small interval is less likely to be reflected by the light reflection portions. Accordingly, the amount of light exiting from the plate surface of the guide plate is equalized in the plane, and uneven brightness is less likely to occur. 
     (3) The light sources may further include a plurality of arrangement interval constant light sources that are located further away from the board attachment member than the arrangement interval variation light sources and may be arranged such that the intervals between the arrangement interval constant light sources are constant regardless of the distance from the board attachment member. If the arrangement interval between the light sources is too small, the amount of light entering through the end surface of the light guide plate may partially increase and this may cause a bright portion. However, as described above, the arrangement interval constant light sources, which are located further away from the board attachment member than the arrangement interval variation light sources, are arranged at the constant intervals regardless of the distance from the board attachment member. Therefore, the arrangement interval is less likely to be too small and thus uneven brightness is further less likely to occur. 
     (4) The arrangement interval variation light sources may be arranged such that the intervals therebetween continuously and gradually decrease as the distance from the board attachment member increases. With the above configuration, the amount of incident light to the end surface of the light guide plate further gradually varies according to the distance from the board attachment member with respect to the arrangement direction of the light sources. Accordingly, dark portions are less likely to occur and thus uneven brightness is further less likely to occur. 
     (5) The board attachment member may be located at a substantially middle portion of the light source board with respect to an arrangement direction of the light sources. In this configuration in which the board attachment member is arranged in the substantially middle portion of the light source board with respect to the arrangement direction of the light sources, if a dark portion where the amount of light entering through the end surface of the light guide plate is locally small is caused, the dark portion is more likely to be noticeable. However, in this configuration, the arrangement interval variation light sources are arranged such that the intervals therebetween gradually vary according to the distance from the board attachment member. Therefore, the dark portion is less likely to be caused at the middle portion of the light guide plate, and thus uneven brightness is less likely to occur. Further, since the board attachment member is arranged at the substantially middle portion of the light source board, the light source board can extend or shrink according to thermal expansion or thermal contraction. Accordingly, deformation such as warping or deflection is less likely to occur. 
     (6) One of outer peripheral surfaces of the light guide plate may be a light source opposed surface opposite the light sources and another outer peripheral surface may be a light source non-opposed surface that is not opposite the light sources. In this configuration, only one end surface of the light guide plate among the outer peripheral surfaces thereof is the light source entrance surface and the others are the light source non-opposed surfaces. Therefore, a larger amount of light tends to enter through the light entrance surface compared to a configuration in which two or more end surfaces of a light guide plate are the light entrance surfaces. If a dark portion where the amount of light entering through the end surface of the light guide plate is locally small is caused, the dark portion is more likely to be noticeable. However, in the above embodiment, the arrangement interval variation light sources are arranged such that the intervals therebetween gradually vary according to the distance from the board attachment member. Therefore, the dark portion is less likely to be caused at the middle portion of the light guide late and thus uneven brightness is less likely to occur. 
     (7) The light sources may be arranged in symmetrical with respect to the board attachment member on the light source board. In this configuration, the light sources are arranged in symmetrical with respect to the board attachment member. Therefore, the amount of light entering through the end surface of the light guide plate symmetrically varies according to the arrangement of the light sources, and thus uneven brightness is less likely to occur. 
     (8) The lighting device may further include light reflection portions configured to reflect light in the light guide plate toward a light exiting side to increase light exiting from the plate surface of the light guide plate and may be arranged such that an area distribution of the light reflection portions in a plane of the plate surface of the light guide plate decreases along an arrangement direction of the light sources as the distance from the board attachment member increases. The light reflection portions may be symmetrical with respect to the board attachment member along the arrangement direction of the light sources. In this configuration, the light reflection portions, which are configured to reflect light inside the light guide plate toward the light emitting side, are arranged such that the area distribution thereof in the plane of the plate surface of the light guide plate decreases as the distance from the board attachment member increases in the arrangement direction of the light sources. Further, the area distribution of the light reflection portions is symmetric with respect to the board attachment member in the arrangement direction of the light sources. Therefore, light from the light sources that are arranged at the relatively larger interval is more likely to be reflected by the light reflection portions, and light from the light sources that are arranged with the relatively smaller interval therebetween is less likely to be reflected by the light reflection portions. Further, a distribution of an overall amount of the reflected light is symmetrical as described above. Accordingly, light exiting through the plate surface of the light guide plate is further equalized in the plane and thus uneven brightness is further less likely to occur. 
     (9) A projection height of the board attachment member from the light source board may be smaller than a projection height of the light sources from the light source board. With this configuration, light from the light sources is less likely to be blocked by the board attachment member and uneven brightness is further less likely to occur. 
     (10) The lighting device may further include a chassis holding the light source board and the light guide plate. The chassis may be the mount member. With this configuration, the light source board can be attached to the mount member with the board attachment member. 
     Next, to solve the above problem, a display device according to this invention may include the above-described lighting device and a display panel configured to provide display using light from the lighting device. 
     With this configuration, uneven brightness is less likely to occur in the lighting device that provides light to the display panel. Accordingly, high quality display can be achieved. 
     The display panel may be a liquid crystal panel. The display device as a liquid crystal display device has a variety of applications, such as a television display or a personal-computer display. In particular, it is suitable for a large screen display. 
     Advantageous Effect of the Invention 
     According to this invention, uneven brightness is reduced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded perspective view illustrating a general configuration of a television device according to a first embodiment of this invention. 
         FIG. 2  is an exploded perspective view illustrating a general configuration of a liquid crystal display device. 
         FIG. 3  is a cross-sectional view taken along a short-side direction of the liquid crystal display device. 
         FIG. 4  is a plan view illustrating an arrangement configuration of a chassis, a light guide plate, and an LED board in a backlight unit included the liquid crystal display device. 
         FIG. 5  is a cross-sectional view taken along line v-v of  FIG. 4 . 
         FIG. 6  is a graph indicating variations in an area ratio of dots included in light reflection portions of the light guide plate in an X-axis direction. 
         FIG. 7  is a graph indicating variations in the area ratio of the dots included in the light reflection portions of the light guide plate in a Y-axis direction. 
         FIG. 8  is a plan view illustrating an arrangement configuration of a chassis, a light guide plate, and an LED board in a backlight unit according to a second embodiment of this invention. 
         FIG. 9  is a graph indicating variations in an area ratio of dots included in light reflection portions of a light guide plate in an X-axis direction. 
         FIG. 10  is a plan view illustrating an arrangement configuration of a chassis, a light guide plate, and an LED board in a backlight unit according to a third embodiment of this invention. 
         FIG. 11  is a graph indicating variations in an area ratio of dots included in light reflection portions of a light guide plate in an X-axis direction. 
         FIG. 12  is a plan view illustrating an arrangement configuration of a chassis, a light guide plate, and an LED board in a backlight unit according to a fourth embodiment of this invention. 
         FIG. 13  is a graph indicating variations in an area ratio of dots included in light reflection portions of a light guide plate in a Y-axis direction. 
         FIG. 14  is a plan view illustrating an arrangement configuration of a chassis, a light guide plate, and an LED board in a backlight unit according to a fifth embodiment of this invention. 
         FIG. 15  is a graph indicating variations in an area ratio of dots included in light reflection portions of a light guide plate in a Y-axis direction. 
         FIG. 16  is a cross-sectional view illustrating a cross-sectional configuration of a chassis, an LED board, and a clip member according to a sixth embodiment of this invention. 
         FIG. 17  is an exploded perspective view illustrating a general configuration of a television device and a liquid crystal display device according to a seventh embodiment of this invention. 
         FIG. 18  is an exploded perspective view illustrating a general configuration of a liquid crystal display unit of a liquid crystal display device. 
         FIG. 19  is a cross-sectional view taken along a short-side direction of a liquid crystal display device. 
         FIG. 20  is a plan view illustrating an arrangement configuration of a chassis, a light guide plate, and an LED board in a backlight unit according to an eighth embodiment of this invention. 
         FIG. 21  is a cross-sectional view illustrating a cross-sectional configuration of a chassis, and LED board, and a screw member according to a ninth embodiment of this invention. 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     First Embodiment 
     A first embodiment of this invention will be described with reference to  FIGS. 1 to 7 . According to this embodiment, a liquid crystal display device  10  will be described. An X-axis, a Y-axis and a Z-axis are present in some drawings. The axes in each drawing correspond to the respective axes in other drawings. An upper side and a lower side in  FIG. 3  correspond to a front side and a rear side, respectively. 
     As illustrated in  FIG. 1 , a television device TV according to this embodiment includes the liquid crystal display device  10 , front and rear cabinets Ca and Cb that hold the liquid crystal display device  10  therebetween, a power source P, a tuner T, and a stand S. An overall shape of the liquid crystal display device (a display device)  10  is a landscape rectangular (longitudinal). The liquid crystal display device  10  is held in a vertical position. As illustrated in  FIG. 2 , the liquid crystal display device  10  includes a liquid crystal panel  11  as a display panel and a backlight unit (a lighting device)  12 . The liquid crystal panel  11  and the backlight unit  12  are held with a bezel  13  having a frame-like shape. 
     As illustrated in  FIG. 2 , the liquid crystal panel has a landscape rectangular shape (rectangular and longitudinal) in a plan view and includes a pair of glass substrates and liquid crystals. The substrates having high light transmissivity are bonded together with a predetermined gap therebetween. The liquid crystals are sealed between the substrates. On one of the substrates (an array substrate), switching components (e.g., TFTs), pixel electrodes and an alignment film are arranged. The switching components are connected to source lines and gate lines that are perpendicular to each other. The pixel electrodes are connected to the switching components. On the other substrate (a CF substrate), a color filter, common electrodes, and an alignment film are arranged. The color filter has color sections such as R (red), G (green) and B (blue) color sections that are arranged in a predetermined pattern. The liquid crustal panel  11  includes a display area and a non-display area. The display area is an inner area of a screen in which images are displayed. The non-display area is an outer area of the screen around the display area and has a frame-like shape. Polarizing plates are arranged on outer sides of the substrates. 
     As illustrated in  FIG. 2 , the backlight unit  12  includes a chassis  14  and optical members  15 . The chassis  14  having a substantially tray-like shape includes a light exit portion  14   c  that opens to the front side (a light exit side, a liquid crystal panel  11  side). The optical members  15  cover the light exit portion  14   c . The chassis  14  holds LEDs (Light Emitting Diodes)  17  provided as light sources, an LED board (light source board)  18  on which the LEDs  17  are mounted, a light guide plate  19 , a frame (a holding member)  16 , and a screw member (a board attachment member)  22 . The light guide plate  19  is configured to guide light from the LEDs  17  toward the optical members  15  (toward the liquid crystal panel  11 ). The frame  16  presses the light guide plate  19  and the optical members  15  from the front side. The screw member  22  fixes the LED board  18  to the chassis (a mount member)  14 . The LED board  18  is arranged at one of long-side end portions (on a front side in  FIGS. 2 and 4  or a left side in  FIG. 3 ) of the backlight unit  12 , and accordingly, the LEDs  17  mounted on the LED board  18  are located locally close to one of long-side end portions of the liquid crystal panel  11 . The backlight unit  12  according to this embodiment is so-called a single-edge-light type (or a side-light type) backlight in which light enters the light guide plate  19  only through one side of the light guide plate  19 . Hereinafter, components of the backlight unit  12  will be described in detail. 
     The chassis  14  is made of a metal plate such as an aluminum plate and an electrolytic zinc-coated steel sheet (SECC). As illustrated in  FIGS. 2 and 4 , similar to the liquid crystal panel  11 , the chassis  14  has a landscape rectangular shape in a plan view. A long-side direction and a short-side direction of the chassis  14  correspond to the X-axis direction (the horizontal direction) and the Y-axis direction (the vertical direction), respectively. The chassis  14  includes a bottom plate  14   a  having a landscape rectangular shape and side plates  14   b  extending from long-side and short-side ends of the bottom plate  14   a . The LED board  18  is attached to one of the side plates  14   b  on the long side (on the front side in  FIGS. 2 and 4  or on the left side in  FIG. 3 ) of the chassis  14 . The frame  16  and the bezel  13  can be fixed to the side plates  14   b  with screws. 
     As illustrated in  FIG. 2 , similar to the liquid crystal panel  11  and the chassis  14 , the optical members  15  have a landscape rectangular shape in a plan view. The optical members  15  are placed on a front surface (a light exit side surface) of the light guide plate  19  and located between the liquid crystal panel  11  and the light guide plate  19 . Light receives predetermined optical effects while passing through the optical members  15  and exits toward the liquid crystal panel  11 . The optical members  15  include multiple sheet-like members (three sheets in this embodiment) which are overlaid with each other. Each optical member  15  may be selected from a diffuser sheet, a lens sheet, and a reflecting type polarizing sheet, whatever is appropriate. In  FIG. 3 , the optical members  15  including three sheets are simplified and illustrated as one sheet. 
     As illustrated in  FIG. 2 , the frame  16  has a frame shape extending along outer edge portions of the light guide plate  19  and holds down substantially the entire edge portions of the light guide plate  19  from the front side. The frame  16  is made of synthetic resin. A front surface of the frame  16  may be in black so as to have light blocking properties. As illustrated in  FIG. 3 , a first reflection sheet  20  that reflects light are attached on an inner surface of one of long-side portions of the frame  16  opposite the LED board  18  (the LEDs  17 ). The first reflection sheet  20  extends over substantially an entire length of the long-side portion of the frame  16 . The first reflection sheet  20  covers an end portion of the light guide plate  19  on an LED  17  side and the LED board  18  from the front side. The frame  16  receives outer edge portions of the liquid crystal panel  11  from the rear side. 
     As illustrated in  FIGS. 3 and 4 , each of the LEDs  17  includes an LED chip that is arranged on a board fixed on the LED board  18  and sealed with resin. The LED chip mounted on the board has one main light emission wavelength. Specifically, the LED chip that emits light in a single color of blue is used. The resin that reals the LED chip contains phosphors dispersed therein. The phosphors emit light in a predetermined color when excited by blue light emitted from the LED chip. Overall color of light emitted from the LED  17  is white. The phosphors may be selected, as appropriate, from yellow phosphors that emit yellow light, green phosphors that emit green light, and red phosphors that emit red light. The phosphors may be used in combination of the above phosphors. The LED  17  includes a main light-emitting surface  17   a  that is opposite from a mount surface of the LED  17  on which the LED board  18  is mounted. Namely, the LED  17  is a top-surface-emitting type LED. 
     As illustrated in  FIGS. 2 and 4 , the LED board  18  has an elongated plate-like shape extending in the long-side direction (the X-axis direction, a long-side direction of a light entrance surface  19   b  of the light guide plate  19 ) of the chassis  14 . The LED board  18  is arranged in the chassis  14  such that plate surfaces of the LED board  18  are parallel to the X-Z plane, i.e., perpendicular to plate surfaces of the liquid crystal panel  11  and the light guide plate  19  (the optical members  15 ). Namely, the long-side direction (a length direction) and the short-side direction (a width direction) of the plate surfaces of the LED board  18  correspond to the X-axis direction and the Z-axis direction, respectively. A plate-thickness direction of the LED board  18  perpendicular to the plate surfaces thereof corresponds to the Y-axis direction. The board of the LED board  18  may be formed of a synthetic resin (a phenolic paper or a glass epoxy resin, for example). 
     As illustrated in  FIGS. 3 and 4 , the LED board  18  includes a mount surface  18   a  on which the LEDs  17  are surface-mounted. The mount surface  18   a  is one of the plate surfaces that faces an inner side, namely, a surface of the LED board  18  that faces the light guide plate  19  (a surface opposite the light guide plate  19 ). The LEDs  17  are arranged apart from each other in a line (i.e., linearly) on the mount surface  18   a  of the LED board  18  along the long-side direction of the LED board  18  (the X-axis direction). Specifically, ten LEDs  17  are arranged at predetermined intervals. In other words, multiple LEDs  17  are arranged at intervals in each of the long-side end portions of the backlight unit  12  along the long-side direction. An arrangement direction of the LEDs  17  corresponds to the length direction of the LED board  18  (the X-axis direction). The arrangement of the LEDs  17  will be described later. A metal-film trace (not illustrated), such as a copper-foil trace, is formed on the mount surface  18   a  of each LED board  18 . The metal-film trace extends in the X-axis direction and crosses over a group of the LEDs  17  so as to connect the adjacent LEDs  17  in series. Terminals at ends of the trace are connected to an external LED drive board (not illustrated), and driving power is supplied to the LEDs  17  therethrough. 
     As illustrated in  FIGS. 4 and 5 , the LED board  18  and the chassis  14  are fixed to each other with a screw member  22  such that a plate surface of the LED board  18  on an outer side (a side opposite to the mount surface  18   a  on which the LEDs  17  are mounted) is in contact with an inner surface of one of the side plates  14   b  that is on the long side of the chassis  14 . The LED board  18  includes a screw through hole (a board attachment member through hole)  18   b  in a substantially middle portion of the LED board  18  with respect to the length direction (the X-axis direction). The screw member  22  is inserted through the screw through hole  18   b . The screw through hole  18   b  is formed in the substantially middle portion of the LED board  18  with respect to the width direction (the Y-axis direction) of the LED board  18 , and disposed apart from the trace. The long-side side plate  14   b  of the chassis  14  to which the LED board  18  is attached includes a screw attachment hole (a board attachment member attachment hole)  14   b   1 . The screw attachment hole  14   b   1  is formed through a substantially middle portion of the side plate  14   b  with respect to the length direction so as to communicate with the screw through hole  18   b . The screw member  22  that is screwed into the screw through hole  18   b  is further screwed into the screw attachment hole  14   b   1 . The screw member  22  includes a shaft portion  22   a  and a head portion  22   b . The shaft portion  22   a  having a substantially post shape includes a screw thread that is formed on an outer peripheral surface of the shaft portion  22   a . The head portion  22   b  having a substantially disk-like shape continues to one of end portions of the shaft portion  22   a . The screw thread of the shaft portion  22   a  is screwed into the screw attachment hole  14   b   1  of the side plate  14   b  of the chassis  14 , and thus the head portion  22   b  and the side plate  14   b  can hold the LED board  18  therebetween. A projection height (a thickness dimension of the heat portion  22   b ) of the screw member  22  from the mount surface  18   a  of the LED board  18  is smaller than a protrusion height (a distance from the mount surface  18   a  to the main light-emitting surface  17   a ) of the LED  17  from the mount surface  18   a  of the LED board  18 . Therefore, light exiting from the LED  17  through the main light-emitting surface  17   a  is less likely to be blocked by the screw member  22 . As described above, the LED board  18 , which is attached to the long-side side plate  14   b  of the chassis  14 , is located on the left side in  FIG. 3  with a predetermined space apart from a long-side end portion of the light guide plate  19 . An arrangement direction in which the LEDs  17  and the LED board  18  and the light guide plate  19  are arranged substantially corresponds to the Y-axis direction. Accordingly, a light axis of each LED  17 , that is, a traveling direction of rays of light having the highest light intensity substantially corresponds to the Y-axis direction (a direction along the plate surface of the liquid crystal panel  11 ). 
     The light guide plate  19  is made of substantially transparent (high transmissivity) synthetic resin (e.g. acrylic resin or polycarbonate such as PMMA) that has a refractive index sufficiently higher than that of the air. As illustrated in FIG.  2 , the light guide plate  19  has a landscape rectangular shape in a plan view similar to the liquid crystal panel  11  and the chassis  14 . The light guide plate  19  is a plate member having a thickness that is larger than that of the optical members  15 . A long-side direction and a short-side direction of the plate surfaces of the light guide plate  19  correspond to the X-axis direction and the Y-axis direction, respectively. A thickness direction of the light guide plate  19  that is perpendicular to the plate surfaces of the light guide plate  19  corresponds to the Z-axis direction. As illustrated in  FIG. 3 , the light guide plate  19  is arranged right behind the liquid crystal panel  11  and the optical members  15  in the chassis  14 . The light guide plate  19  includes long-side end surfaces included in outer peripheral end surfaces thereof. One of the long-side end surfaces (the front side in  FIGS. 2 and 4  or the left side in  FIG. 3 ) of the light guide plate  19  is opposite the LEDs  17  of the LED board  18  that are arranged in one of the long-side end portions of the chassis  14 . Namely, an arrangement direction between the LEDs  17  (or the LED board  18 ) and the light guide plate  19  corresponds to the Y-axis direction, and an arrangement direction between the optical members  15  (or the liquid crystal panel  11 ) and the light guide plate  19  corresponds to the Z-axis direction. The both arrangement directions are perpendicular to each other. The light guide plate  19  is configured to guide the light, which is emitted from the LEDs  17  in the Y-axis direction and enters the light guide plate  19 , toward the optical members  15  (on the front side). 
     As illustrated in  FIGS. 2 and 4 , the light guide plate  19  has a plate-like shape extending along plate surfaces of the bottom plate  14   a  of the chassis  14  and the optical members  15 . The plate surfaces of the light guide plate  19  are parallel to the X-Y plane. One of the plate surfaces (a surface opposite the optical members  15 ) of the light guide plate  19  on the front side is a light exit surface  19   a . Light that is inside the light guide plate  19  exits through the light exit surface  19   a  toward the optical members  15  and the liquid crystal panel  11 . The outer peripheral end surfaces of the light guide plate  19  that are adjacent to the plate surfaces thereof include the long-side end surfaces elongated along the X-axis direction (the arrangement direction of the LEDs  17  or the long-side direction of the LED board  18 ). One of the long-side end surfaces (located on the front side in the  FIGS. 2 and 4 ) is opposite the LEDs  17  (or the LED board  18 ) with a predetermined space therebetween and is the light entrance surface  19   b  through which light emitted from the LEDs  17  enters the light guide plate  19 . Since the light entrance surface  19   b  is opposite the LEDs  17 , the light entrance surface  19   b  is referred to as an LED opposed surface (a light source opposed surface). On the other hand, among the outer peripheral end surfaces of the light guide plate  19  that are adjacent to the plate surfaces of the light guide plate  19 , three surfaces except the above-described light entrance surface  19   b  (another long-side surface (located on a far end side in  FIGS. 2 and 4 ) and short-side end surfaces) are LED non-opposed surfaces (light source non-opposed surfaces)  19   d  that are not opposite the LEDs  17 . A distance between the light entrance surface  19   b  and each opposed LED  17  is substantially the same. The light entrance surface  19   b  is parallel to the X-axis direction (the arrangement direction of the LEDs  17 ) and the Z-axis direction. In other words, the light entrance surface  19   b  is parallel to the plate surfaces of the LED board  18 , and substantially perpendicular to the light exit surface  19   a . An arrangement direction between the LEDs  17  and the light entrance surface  19   b  corresponds to the Y-axis direction, and parallel to the light exit surface  19   a.    
     As illustrated  FIG. 3 , a second reflection sheet  21  is disposed on the rear surface of the light guide plate  19 , that is, a plate surface (a surface opposite to the bottom plate  14   a  of the chassis  14 )  19   c  away from the light exit surface  19   a  of the light guide plate  19  so as to cover about the entire surface. The second reflection sheet  21  is configured such that light exiting the light guide plate  19  through the plate surface  19   c  toward the rear side is reflected thereby toward the front side. The second reflection sheet  21  is sandwiched between the bottom plate  14   a  of the chassis  14  and the light guide plate  19 . An end portion of the second reflection sheet  21  on a light entrance surface  19   b  side of the light guide plate  19  extends outward from the light entrance surface  19   b  of the light guide plate  19 , that is, toward an LEDs  17  side. An extended end portion of the second reflection sheet  21  faces the first reflection sheet  20  that is attached to the frame  16 . The LEDs  17  and the light entrance surface  19   b  define a space in between, and the space is positioned between the first reflection sheet  20  and the second reflection sheet  21 . Therefore, light that travels from the LEDs  17  toward the light entrance surface  19   b  is repeatedly reflected by the first reflection sheet  20  and the second reflection sheet  21 , and thus the light efficiently enters the light guide plate  19 . On the plate surface  19   c  of the light guide plate  19  that is opposite to the light exit surface  19   a , light reflection portions  23  are provided. The light reflection portions  23  are for reflecting rays of light inside the light guide plate  19  toward the light exit surface  19   a  to increase the rays of light exiting through the light exit surface  19   a . The light reflection portions  23  are located between the plate surface  19   c  of the light guide plate  19  that is opposite to the light exit surface  19   a  and the second reflection sheet  21 . 
     As illustrated in  FIG. 4 , the light reflection portions  23  are formed by printing a light reflective material on the plate surface  19   c  of the light guide plate  19  away from the light exit surface  19   a . Namely, the light reflection portions  23  may be referred to as light reflective prints. The light reflective material used for the light reflection portions  23  is a white ink (or a paste) containing metal oxide such as titanium oxide. The light reflection portions  23  are configured to diffusely reflect the rays of light entering the light guide plate  19  and reaching the plate surface  19   c  away from the light exit surface  19   a  toward the light exit surface  19   a . The light reflection portions  23  are further configured to vary an angle of incidence at the light exit surface  19   a  compared with an angle of incidence of light that is fully reflected at the light exit surface  19   a . With this configuration, more rays of light, the angles of incidence of which do not exceed the critical angle exist and thus the amount of light that exits through the light exit surface  19   a  increases. The light reflection portions  23  may be formed on the light guide plate  19  by printing methods including silk printing (screen printing) and inkjet printing. With the silk printing, production cost is reduced when the light guide plates  19  are mass-produced. With the inkjet printing, the light reflection portions  23  can be formed with high accuracy even if the light reflection portions  23  are formed in a complex pattern. 
     The backlight unit  12  according to this embodiment is an edge-light type backlight unit in which the LEDs  17  are locally arranged in one end portion of the chassis  14 . As illustrated in  FIGS. 4 and 5 , the screw member  22  that fixes the LED board  18  including the LEDs  17  to the chassis  14  is arranged between the adjacent LEDs  17  on the LED board  18 . In this configuration, a space for the screw member  22  provided between the adjacent LEDs  17  is likely to increase an interval (an arrangement interval) between the adjacent LEDs  17  arranged with the screw member  22  in between. If only the interval between specific LEDs is large, an amount of light entering the light guide plate through a part of the light entrance surface opposed to the specific LEDs is locally small, and this may cause a dark portion. According to this embodiment, as illustrated in  FIG. 4 , the LEDs  17  arranged in a line at intervals on the LED board  18  include arrangement interval variation LEDs (arrangement interval variation light sources)  24 . The arrangement interval variation LEDs  24  are arranged such that intervals P 1  to P 3  therebetween decrease as a distance from the screw member  22  increases. Since the LEDs  17  include the arrangement interval variation LEDs  24 , the intervals P 1  to P 3  between the adjacent LEDs  17  gradually vary according to the distance from the screw member  22 . Accordingly, an amount of light entering through the light entrance surface  19   b  gradually varies according to the distance from the screw member  22 . Therefore, the above-described dark portion is less likely to be caused. Next, the intervals between the LEDs  17  will be described in detail. 
     As illustrated in  FIG. 4 , the arrangement interval variation LEDs  24  include a total of six LEDs that are a pair of first LEDs (first light sources)  24   a , a pair of second LEDs (second light sources)  24   b , and a pair of third LEDs (third light sources)  24   c . The first LEDs  24   a  are arranged adjacent to each other with the screw member  22  in between. The screw member  22  is located in the substantially middle portion of the LED board  18  with respect to the length direction (the X-axis direction or the arrangement direction of the LEDs  17 ). Each of the second LEDs  24   b  is on an outer side (a side opposite to a screw member  22  side) with respect to and adjacent to the corresponding first LED  24   a . Each of the third LEDs  24   c  is on an outer side (the side opposite to the screw member  22  side or a side opposite to a first LED  24   a  side) with respect to and adjacent to the corresponding second LED  24   b . Among the LEDs  17 , the first LEDs  24   a  are located at the shortest distance from the screw member  22  on the LED board  18  in the X-axis direction. In other words, the first LEDs  24   a  are located closest to the middle portion of the LED board  18  with respect to the length direction of the LED board  18 . A distance from the screw member  22  (the middle portion of the LED board  18  in the length direction) to the second LED  24   b  and the third LED  24   c  in the X-axis direction increases in this sequence. The third LEDs  24   c  are arranged closest to respective ends of the LED board  18  among the arrangement interval variation LEDs  24 . Herein, when “P 1 ” denotes the interval between the pair of first LEDs  24   a , “P 2 ” denotes the interval between the first LED  24   a  and the second LED  24   b , and “P 3 ” denotes the interval between the second LED  24   b  and the third LED  24   c , the size relation thereof satisfies an inequality of “P 1 &gt;P 2 &gt;P 3 ”. P 1  has a maximum value and P 3  has a minimum value. Specifically, a dimension of P 1  is about 5 mm, a dimension of P 2  is about 4 mm, and a dimension of P 3  is about 3 mm. As is just described, the arrangement interval variation LEDs  24  are arranged on the LED board  18  such that the intervals P 1  to P 3  therebetween gradually decrease as the distance from the screw member  22  increases in the X-axis direction (the arrangement direction of LEDs  17 ). The first LEDs  24   a , the second LEDs  24   b , and the third LEDs  24   c  are arranged in symmetrical with respect to a symmetry line that passes through the middle portion (or the screw member  22 ) of the LED  18  in the length direction. 
     As illustrated in  FIG. 4 , the LEDs  17  according to this embodiment include arrangement interval constant LEDs (arrangement interval constant light sources)  25 . The arrangement interval constant LEDs  25  are located further away from the screw member  22  than the arrangement interval variation LEDs  24 . The arrangement interval constant LEDs  25  are arranged such that an interval P 4  and P 5  therebetween is substantially constant regardless of the distance from the screw member  22 . The arrangement interval constant LEDs  25  include a total of four LEDs that are a pair of fourth LEDs (fourth light sources)  25   a  and a pair of fifth LEDs (fifth light sources)  25   b . Each of the fourth LEDs  25   a  is on an outer side (a side opposite to the screw member  22  side or a side opposite to a second LED  24   b  side) with respect to and adjacent to the corresponding third LED  24   c  that is the arrangement interval variation LED  24 . Each of the fifth LEDs  25   b  is on an outer side (a side opposite to the screw member  22  side or opposite to a third LED  24   c  side) with respect to and adjacent to the corresponding fourth LED  25   a . The distance in the X-axis direction from the fifth LED  25   b  to the screw member  22  (the middle portion of the LED board  18  in the length direction) is longer than the distance from the fourth LED  25   a  to the screw member  22  on the LED board  18 . The fourth LEDs  25   a  are located relatively close to the middle portion (close to the screw member  22 ) of the LED board  18  among the arrangement interval constant LEDs  25 . The fifth LEDs  25   b  are arranged closest to respective ends of the LED board  18  among all the LEDs  17 . Herein, when “P 4 ” denotes the interval between the third LED  24   c  and the fourth LED  25   a  and “P 5 ” denotes the interval between the fourth LED  25   a  and the fifth LED  25   b , an equality of “P 4 =P 5 ” is satisfied while an inequality of “P 3 &gt;P 4 =P 5 ” is satisfied. Accordingly, among all of the LEDs  17  (the arrangement interval variation LEDs  24  and the arrangement interval constant LEDs  25 ), the arrangement interval takes a maximum value at “P 1 ” and takes a minimum value at “P 4  and P 5 ”. Specifically, a dimension of P 4  and a dimension of P 5  are about 2 mm and substantially equal. As is just described, the arrangement interval constant LEDs  25  are arranged on the LED board  18  such that the intervals P 4  and P 5  therebetween are substantially equal (less likely to vary) regardless of the distance from the screw member  22 . The fourth LEDs  25   a  and the fifth LEDs  25   b  are arranged in symmetrical with respect to the symmetry line that passes through the middle portion (or the screw member  22 ) of the LED board  18  in its length direction. 
     According to the arrangement of the LEDs  17  as described above, the light reflection portions  23  for directing more light to the outside of the light guide plate  19  have following configurations. As illustrated in  FIG. 4 , the light reflection portions  23  include a number of dots formed with ink and dispersedly arranged with predetermined distribution within the plate surface  19   c  opposite from the light exiting surface  19   a  of the light guide plate  19 . The dots include area variation dots  26  that are arranged such that an area of the dots  26  decreases as the distance from the screw member  22  in the X-axis direction increases in the area distribution of the dots  26  within a plane of the plate surface (the light exit surface  19   a , the plate surface  19   c ) of the light guide plate  19 . Further, in addition to the area variation dots  26 , the dots included in the light reflection portions  23  include area constant dots  27 . The area constant dots  27  are arranged such that an area of the dots  27  is constant regardless of the distance from the screw member  22  in the X-axis direction in the area distribution of the dots  27  within the plane of the plate surface of the light guide plate  19 . The area variation dots  26  and the area constant dots  27  will be described in detail next. 
     As illustrated in  FIGS. 4 and 6 , the area variation dots  26  are arranged in a middle portion of the plate surface of the light guide plate  19  with respect to the long-side direction (the X-axis direction) of the light guide plate  19 , and not arranged in end portions thereof. The area variation dots  26  are patterned as follows. An area ratio of the area variation dots  26  per unit area in the plane of the plate surface (the light exit surface  19   a , the plate surface  19   c ) of the light guide plate  19  takes a maximum value in the middle portion of the light guide plate  19  with respect to the X-axis direction (the arrangement direction of the LEDs  17 ), that is, a portion of the light guide plate  19  corresponding to the screw member  22  with respect to the X-axis direction. The area ratio of the area variation dots  26  gradually decreases as a distance from the middle portion of the light guide plate  19  toward edges of the light guide plate  19  in the X-axis direction increases. The area ratio takes a minimum value at a portion of the light guide plate  19  corresponding to the third LED  24   c  of the arrangement interval variation LEDs  24  in the X-axis direction. In other words, an arrangement region  26 A of the light guide plate  19  including the area variation dots  26  substantially corresponds to an arrangement region of the LED board  18  including the arrangement interval variation LEDs  24  (the first LEDs  24   a , the second LEDs  24   b , and third LEDs  24   c ). The areas of the area variation dots  26  continuously and gradually decrease as the distance from the screw member  22  in the X-axis direction increases. 
     The first LEDs  24   a  are arranged at the relatively large interval P 1 , and rays of light emitted from the first LEDs  24   a  and entering the light guide plate  19  through the light entrance surface  19   b  are more likely to be reflected by dots having relatively large areas among the area variation dots  26 . On the other hand, the third LED  24   c  is arranged with the relatively small interval P 3 , and rays of light emitted from the third LED  24   c  and entering the light guide plate  19  through the light entrance surface  19   b  are less likely to be reflected by dots having relatively small areas among the area variation dots  26 . Accordingly, in the light exit surface  19   a  of the light guide plate  19 , the amount of light exiting the arrangement region  26 A including the area variation dots  26  is equalized in the plane. 
     As illustrated in  FIGS. 4 and 6 , the area constant dots  27  are arranged in the end portions of the plate surface of the light guide plate  19  with respect to the long-side direction (the X-axis direction) and not arranged in the middle portion thereof. The area constant dots  27  are patterned as follows. An area ratio of the area constant dots  27  per unit area in the plane of the plate surface (the light exit surface  19   a , the plate surface  19   c ) of the light guide plate  19  is substantially constant regardless of the positions in the X-axis direction (the arrangement direction of the LEDs  17 ), that is, regardless of the distance from the screw member  22  in the X-axis direction. The area ratio of the area constant dots  27  takes the minimum value in the plane of the plate surface of the light guide plate  19 . The area constant dots  27  are arranged so as to correspond to the fourth LEDs  25   a  and the fifth LEDs  25   b  included in the arrangement interval constant LEDs  25  with respect to the X-axis direction. In other words, an arrangement region  27 A of the light guide plate  19  including the area constant dots  27  substantially corresponds to an arrangement region of the LED board  18  including the arrangement interval constant LEDs  25  (the fourth LEDs  25   a  and the fifth LEDs  25   b ). Rays of light emitted from the fourth LED  25   a  and the fifth LED  25   b , which are included in the arrangement interval constant LEDs  25 , and entering the light guide plate  19  through the light entrance surface  19   b  are reflected by the area constant dots  27 . Accordingly, in the light exit surface  19   a  of the light guide plate  19 , the amount of light exiting the arrangement region  27 A including the area constant dots  27  is equalized in the plane. The area variation dots  26  and the area constant dots  27  included in the light reflection portion  23  are arranged such that their area distributions are symmetric with respect to a symmetry line passing through the middle portion of the light guide plate  19  with respect to the long-side direction thereof. The area distributions of the area variation dots  26  and the area constant dots  27  are similar to the area distributions of the arrangement interval variation LEDs  24  and the arrangement interval constant LEDs  25  included in the LEDs  17  in the LED board  18 . 
     Next, the area distribution of the light reflection portions  23  in the short-side direction (the Y-axis direction) of the light guide plate  19  will be described. As illustrated in  FIGS. 4 and 7 , an area ratio of the light reflection portions  23  per unit area in the plane of the plate surface of the light guide plate  19  continuously and gradually decreases as a distance from the LEDs  17  (or the light entrance surface  19   b ) in the Y-axis direction increases, and continuously and gradually increases as the distance from the LEDs  17  decreases. A left end of the horizontal axis in  FIG. 7  corresponds to the end portion of the light guide plate  19  on the light entrance surface  19   b  side. A right end of the horizontal axis in  FIG. 7  corresponds to the other end of the light guide plate  19  opposite to the light entrance surface  19   b . Areas of the area constant dots  27  are “constant” only when areas of the dots arranged along the X-axis direction are compared. However, when areas of the dots arranged along the Y-axis direction are compared, the areas continuously and gradually decrease as the distance from the LEDs  17  increases. This configuration is the same for the area variation dots  26 . 
     This embodiment has the above-described configuration, and an operation thereof will be described. When the liquid crystal display device  10  having the above-described configuration is tuned on, driving of the liquid crystal panel  11  is controlled by a panel control circuit (not illustrated), and driving of the LED  17  on the LED board  18  is controlled by driving power provided from an LED drive circuit (not illustrated). Light emitted from each LED  17  is guided by the light guide plate  19  and applied to the liquid crystal panel  11  via the optical members  15 . As a result, images are displayed on the liquid crystal panel  11 . Hereinafter, operations of the backlight unit  12  will be explained. 
     As illustrated in  FIG. 3 , when the LED  17  is turned on, the rays of light emitted from the LED  17  enter the light guide plate  19  through the light entrance surface  19   b . The LED  17  and the light entrance surface  19   b  are arranged with a predetermined space therebetween. The space is provided between the first reflection sheet  20  on the front side and the extended end portion of the second reflection sheet  21  on the rear side. Therefore, the rays of light from the LED  17  are repeatedly reflected by the both reflection sheets  20  and  21  and thus the rays of light efficiently enter through the light entrance surface  19   b . The rays of light that enter through the light entrance surface  19   b  are totally reflected by an interface between the light guide plate  19  and an external air layer or by the second reflection sheet  21 . Furthermore, the rays of light are diffusely reflected by the light reflection portions  23  while traveling through the light guide plate  19 . With this configuration, the incident angles of the rays of light to the light exit surface  19   a  do not exceed the critical angle and thus more rays of light exit from the light exit surface  19   a.    
     As illustrated in  FIG. 4 , the LED board  18  on which the LEDs  17  are mounted is attached to the chassis  14  with the screw member  22 . The screw member  22  is located at the middle portion of the LED board  18  with respect to the long-side direction of the LED board  18 . Because the screw  22  is arranged between the adjacent LEDs  17 , the interval P 1  between the adjacent LEDs  17  (the first LEDs  24   a ) tends to be large. This may cause a partial dark portion in the light entrance surface  19   b  through which light from the LEDs  17  (the first LEDs  24   a ) enters the light guide plate  19 . However, in this embodiment, the LEDs  17  include the arrangement interval variation LEDs  24 , which are arranged such that the intervals P 1  to P 3  therebetween decrease as the distance from the screw member  22  increases. Therefore, the amount of light emitted from at least the arrangement interval variation LEDs  24  and entering the light guide plate  19  through the light entrance surface  19   b  per unit area gradually varies according to the distance from the screw member  22 . Accordingly, a partial dark portion that is caused due to the screw member  22  is less likely to be caused in the light entrance surface  19   b  or the light exit surface  19   a  of the light guide plate  19 , and thus uneven brightness is less likely to occur in the light exiting the backlight unit  12 . As a result, a high quality display image can be displayed on the liquid crystal panel  11 . 
     Specifically, the arrangement interval variation LEDs  24  are arranged as follows. The interval P 1  between the first LEDs  24   a  that are located closest to the screw member  22  has the maximum value. The interval P 2  between the first LED  24   a  and the second LED  24   b  adjacent to the first LED  24   a  has a smaller value next to P 1 . The interval P 3  between the second LED  24   b  and the third LED  24   c  adjacent to the second LED  24   b  has a smaller value next to the interval P 2 . The intervals P 1  to P 3  between the arrangement interval variation LEDs  24  vary continuously and gradually according to the distance from the screw member  22 . Light from the LED  17  spreads from the main light-emitting surface  17   a  to a certain range with respect to the X-Z plane and reaches the light entrance surface  19   b  of the light guide plate  19 . The amount of incident light per unit area in the light entrance surface  19   b  tends to decrease as the interval between the adjacent LEDs  17  decreases, and on the contrary, the amount of incident light per unit area in the light entrance surface  19   b  tends to increase as the interval between the adjacent LEDs  17  increases. As described above, the intervals P 1  to P 3  between the arrangement interval variation LEDs  24  gradually vary. Therefore, the amount of incident light per unit area in the light entrance surface  19   b  continuously and gradually varies according to the distance from the screw member  22 . If the amount of incident light per unit area is partially small, a partial dark portion may be caused. However, in this embodiment, the amount of incident light per unit area in the light entrance surface  19   b  continuously and gradually varies, and thus the partial dark portion is less likely to be caused in the light entrance surface  19   b . As a result, uneven brightness is less likely to occur among rays of the light exiting from the light exit surface  19   a  of the light guide plate  19  and the backlight  12 . 
     Further, as illustrated in  FIG. 4 , the LEDs  17  include the arrangement interval constant LEDs  25  that are located further away from the screw member  22  than the arrangement interval variation LEDs  24 . The arrangement interval constant LEDs  25  are arranged at the substantially constant intervals P 4  and P 5  regardless of the distance from the screw member  22 . If compared to a case in which all LEDs are arrangement interval variation LEDs, the interval between the LEDs that are arranged away from the screw member  22  is less likely to be too small in this configuration. Herein, the interval between the adjacent LEDs  17  has an optimum value that achieves an optimum amount of incident light per unit area in the light entrance surface  19   b . The intervals P 1  to P 3  between the arrangement interval variation LEDs  24  are gradually reduced according to the distance from the screw member  22 , and the interval will reach the optimum value. When the interval reaches the optimum value, the arrangement interval constant LEDs  25  that are arranged at constant intervals are arranged. Accordingly, the intervals P 4  and P 5  between the arrangement interval constant LEDs  25  can be maintained to be the optimum value regardless of the distance from the screw member  22 . As a result, uneven brightness is further less likely to occur among rays of light from the light exit surface  19   a  of the light guide plate  19  and the backlight unit  12 . 
     As described above, the light emitted from the LEDs  17  and entering the guide plate  19  through the light entrance surface  19   b  is diffusely reflected by the light reflection portions  23  and exits through the light exit surface  19   a . As illustrated in  FIGS. 4 and 6 , the dots of the light reflection portions  23  include the area variation dots  26 , which are arranged such that the area distribution thereof in the plane of the plate surface (the light exit surface  19   a , the plate surface  19   c ) of the light guide plate  19  becomes smaller as the distance from the screw member  22  in the X-axis direction (the arrangement direction of the LEDs  17 ) increases. The arrangement region  26 A where the area variation dots  26  are arranged corresponds to the arrangement region where the arrangement interval variation LEDs  24  are arranged. Light from each arrangement interval variation LED  24  is reflected by the corresponding area variation dots  26  and thus the amount of light exiting from the light exit surface  19   a  is equalized. Specifically, the first LEDs  24   a  are arranged at the relatively large interval P 1 , and rays of light exited from the first LEDs  24   a  to the light guide plate  19  through the light entrance surface  19   b  are more likely to be reflected by the dots having relatively large areas among the area variation dots  26 . The second LED  24   b  is arranged to have the relatively small interval P 2 , and rays of light emitted from the second LED  24   b  and entering the light guide plate  19  through the light entrance surface  19   b  are less likely to be reflected by the dots having relatively small areas among the area variation dots  26 . The third LED  24   c  is arranged to have the relatively smaller interval P 3 , and rays of light emitted from the third LED  24   c  and entering the light guide plate  19  through the light entrance surface  19   b  are further less likely to be reflected by the dots having relatively smaller areas among the area variation dots  26 . With this configuration, in the light exit surface  19   a  of the light guide plate  19 , the amount of light exiting the arrangement region  26 A including the area variation dots  26  is further effectively equalized in the plane and the uneven brightness is further less likely to occur. 
     As illustrated in  FIGS. 4 and 6 , in addition to the area variation dots  26 , the dots of the light reflection portions  23  include the area constant dots  27 . The area constant dots  27  are arranged such that the area distribution thereof in the plane of the plate surface of the light guide plate  19  is substantially constant regardless of the distance from the screw member  22  in the X-axis direction. The arrangement region  27 A where the area constant dots  27  are arranged substantially corresponds to the arrangement region where the arrangement interval constant LEDs  25  are arranged. Therefore, light from the arrangement constant LEDs  25  is reflected by the area constant dots  27  and thus the amount of light exiting through the light exit surface  19   a  is equalized. Specifically, the fourth LEDs  25   a  and the fifth LEDs  25   b  included in the arrangement interval constant LEDs  25  are arranged at the substantially constant intervals P 4  and P 5 , and thus the amount of light entering through the light entrance surface  19   b  per unit area is substantially constant. The light entering through the light entrance surface  19   b  is reflected by the area constant dots  27  having the substantially constant area. Therefore, the amount of light exiting through the arrangement region  27 A where the arrangement interval constant dots  27  are arranged is equalized in the plane. With this configuration, uneven brightness is further less likely to occur. 
     The LEDs  17  mounted on the LED board  18  generate heat by light emission. The LED board  18  of this embodiment is made of synthetic resin having a coefficient of thermal expansion higher than that of metal. Therefore, an expansion or contraction amount of the LED board  18  due to thermal expansion or thermal contraction is large. However, as illustrated in  FIGS. 4 and 5 , the LED board  18  is attached to the chassis  14  with the screw member  22  at the substantially middle portion of the LED board  18  in the length direction of the LED board  18 . Therefore, the LED board  18  can expand or contract in the length direction or the left and right direction regarding the attachment portion with the screw member  22  as an original point. Accordingly, deformation such as warping or deflection that may occur due to restriction of expansion or contraction is less likely to occur in the LED board  18 . 
     As described above, the backlight unit (the lighting device)  12  according to this embodiment includes the LEDs (the light sources)  17 , the light guide plate  19 , the LED board (the light source board)  18 , the chassis (a mount member)  14 , the screw member (a board attachment member)  22 , the arrangement interval variation LEDs (arrangement interval variation light sources)  24 . The light guide plate  19  includes the end surface (the light entrance surface  19   b ) and the plate surface (the light exit surface  19   a ). The end surface is opposite the LEDs  17 . Light from the LEDs  17  enters the light guide plate  19  through the end surface and exits the light guide plate  19  through the plate surface. The LED board  18  is provided with the LEDs  17  mounted thereto such that the LEDs  17  are arranged at intervals along the end surface of the light guide plate  19 . The chassis  14  is provided with the LED board  18  attached thereto. The screw member  22  is disposed between the LEDs  17  adjacent to each other and attaches the LED board  18  to the chassis  14 . The arrangement interval variation LEDs  24  are included in the LEDs  17  and arranged such that the intervals P 1  to P 3  between the arrangement interval variation LEDs  24  decrease as the distance from the LED board  18  increases. 
     In the above configuration, light emitted from the LEDs  17  enters the light guide plate  19  through the end surface and travels within the light guide plate  19  and then exits the light guide plate  19  through the plate surface. The LED board  18  includes the LEDs  17  mounted thereto such that the LEDs  17  are arranged at intervals along the end surface of the light guide plate  19 . The screw member  22  to attach the LED board  18  to the chassis  14  is disposed between the LEDs  17  that are adjacent to each other. The interval between the adjacent LEDs  17  with the screw member  22  therebetween tends to be large because a space needs to be provided to arrange the screw member  22 . Accordingly, the amount of light entering through the end surface of the light guide plate  19  may be partially small, and a dark portion may be caused. However, as is described earlier, the LEDs  17  include the arrangement interval variation LEDs  24  that are arranged such that the intervals P 1  to P 3  therebetween decrease as the distance from the screw member  22  increases. Therefore, the amount of light traveling from at least the arrangement interval variation LEDs  24  to the end surface of the light guide plate  19  per unit area gradually varies according to the distance from the screw member  22 . Accordingly, a dark portion is less likely to occur at the end surface of the light guide plate  19 , and thus uneven brightness is less likely to occur in the exiting light. 
     The arrangement interval variation LEDs  24  include at least a pair of the first LEDs  24   a , the second LED  24   b , and the third LED  24   c . The first LEDs  24   a  are arranged with the screw member  22  therebetween. The second LEDs  24   b  is arranged adjacent to at least one of the first LEDs  24   a  such that the interval between the at least one of the first LEDs  24   a  and the second LED  24   b  is smaller than the interval between the first LEDs  24   a . The third LEDs  24   c  is arranged adjacent to the second LEDs  24   b  such that the interval between the second LED  24   b  and the third LED  24   c  is smaller than the interval between the at least one of the first LEDs  24   a  and the second LED  24   b . In the above configuration, the intervals gradually decrease in the following sequence: the interval P 1  provided between the first LEDs  24   a  that are arranged with the screw member  22  in between, the interval P 2  provided between the one of the first LEDs  24   a  and the second LED  24   b  adjacent to the one of the first LEDs  24   a , and the interval P 3  provided between the second LED  24   b  and the third LED  24   c  adjacent to the second LED  24   b . Accordingly, the amount of light entering through the end surface of the light guide plate  19  gradually varies according to the distance from the screw member  22 , and thus a dark portion is less likely to occur. 
     The light reflection portions  23  are configured to reflect light in the light guide plate  19  toward a light exit side to increase light exiting from the plate surface of the light guide plate  19  and arranged such that the area distribution of the light reflection portions  23  in the plate of the plate surface of the light guide plate  19  decreases along the arrangement direction of the LEDs  17  as the distance from the screw member  22  increases. In the above configuration, the light reflection portions  23  that are configured to reflect light in the light guide plate  19  toward the light exit side are arranged such that the area distribution thereof in the plane of the plate surface of the light guide plate  19  decreases as the distance from the screw member  22  along the arrangement direction of the LEDs  17  increases. Therefore, light from the LEDs  17  arranged at the relatively large interval P 1  is more likely to be reflected by the light reflection portions  23 , and light from the LEDs  17  arranged at the relatively small interval P 3  is less likely to be reflected by the light reflection portions  23 . Accordingly, the amount of light exiting from the plate surface of the guide plate  19  is equalized in the plane, and thus uneven brightness is less likely to occur. 
     The LEDs  17  include the arrangement interval constant LEDs  25  (the arrangement interval constant light sources) that are located further away from the screw member  22  than the arrangement interval variation LEDs  24  and arranged such that the intervals P 4  and P 5  between the arrangement interval constant LEDs  25  are constant regardless of the distance from the screw member  22 . If the interval between the LEDs  17  is too small, the amount of light entering through the end surface of the light guide plate  19  may partially increase and a bright portion may be caused. However, as described above, the arrangement interval constant LEDs  25 , which are located further away from the screw member  22  than the arrangement interval variation LEDs  24 , are arranged such that the intervals P 4  and P 5  are constant regardless of the distance from the screw member  22 . Therefore, the interval is less likely to be too small and thus uneven brightness is further less likely to occur. 
     The arrangement interval variation LEDs  24  are arranged such that the intervals P 1  to P 3  therebetween continuously and gradually decrease as the distance from the screw member  22  increases. With the above configuration, the amount of incident light to the end surface of the light guide plate  19  further gradually varies according to the distance from the screw member  22  with respect to the arrangement direction of the LEDs  17 . Accordingly, dark portions are less likely to occur and thus uneven brightness is further less likely to occur. 
     The screw member  22  is located at the substantially middle portion of the LED board  18  with respect to the arrangement direction of the LEDs  17 . In this configuration where the screw member  22  is arranged in the substantially middle portion of the LED board  18  with respect to the arrangement direction of the LEDs  17 , if a dark portion where the amount of light entering through the end surface of the light guide plate  19  is locally small is caused, the dark portion is more likely to be noticeable. However, in the above configuration, the arrangement interval variation LEDs  24  are arranged such that the intervals P 1  to P 3  therebetween gradually vary according to the distance from the screw member  22 . Therefore, the dark portion is less likely to be caused at the middle portion of the light guide plate  19 , and thus uneven brightness is less likely to occur. Further, since the screw member  22  is arranged at the substantially middle portion of the LED board  18 , the LED board  18  can extend or shrink according to thermal expansion or thermal contraction. Accordingly, deformation such as warping or deflection is less likely to occur. 
     One of the outer peripheral surfaces of the light guide plate surfaces of the light guide plate  19  is the light entrance surface (the light source opposed surface)  19   b  opposite to the LEDs  17 . Other surfaces thereof are the LED non-opposed surfaces (the light source non-opposed surface)  19   d  of the light guide plate  19  that are not opposite the LEDs  17 . In this configuration, only one end surface of the light guide plate  19  among the outer peripheral surfaces thereof is the light entrance surface  19   b  and the others are the LED non-opposed surfaces  19   d . Therefore, a larger amount of light tends to enter through the light entrance surface  19   b  compared to a configuration in which two or more end surfaces of a light guide plate are the light entrance surfaces. If a dark portion, where the amount of light entering through the end surface of the light guide plate  19  is locally small is caused, the dark portion is more likely to be noticeable. However, in the above embodiment, the arrangement interval variation LEDs  24  are arranged such that the intervals P 1  to P 3  therebetween gradually vary according to the distance from the screw member  22 . Therefore, the dark portion is less likely to be caused at the middle portion of the light guide late  19  and thus uneven brightness is less likely to occur. 
     The LEDs  17  are arranged in symmetrical with respect to the screw member  22  on the LED board  18 . In this configuration, the LEDs  17  are arranged in symmetrical with respect to the screw member  22 . Therefore, the amount of light entering through the end surface of the light guide plate  19  symmetrically varies according to the arrangement of the LEDs  17 , and thus uneven brightness is less likely to occur. 
     The light reflection portions  23  are configured to reflect light in the light guide plate  19  toward the light exit side to increase light exiting from the plate surface of the light guide plate  19 . The light reflection portions  23  are arranged such that an area distribution of the light reflection portions  23  in the plate of the plate surface of the light guide plate  19  decreases along the arrangement direction of the LEDs  17  as the distance from the screw member  22  increases. Further, the light reflection portions  23  are in symmetrical with respect to the screw member  22  along the arrangement direction of the LEDs  17 . In this configuration, the light reflection portions  23 , which are configured to reflect rays of light inside the light guide plate  19  toward the light emitting side, are arranged such that areas of the light reflection portions decrease as the distance from the screw member  22  increases in the arrangement direction of the LEDs  17  in the area distribution of the light reflection portions  23  within a plane of the plate surface of the light guide member. Further, the area distribution of the light reflection portions  23  is symmetrical with respect to the screw member  22  in the arrangement direction of the LEDs  17 . Therefore, light from the LEDs  17  that are arranged at the relatively larger interval P 1  therebetween is more likely to be reflected by the light reflection portions  23 , and light from the LEDs  17  that are arranged at the relatively smaller interval P 3  therebetween is less likely to be reflected by the light reflection portions  23 . Further, a distribution of an overall amount of the reflected light is symmetrical as described above. Accordingly, light exiting through the plate surface of the light guide plate  19  is further equalized in the plane and thus uneven brightness is further less likely to occur. 
     The projection height of the screw member  22  from the LED board  18  is smaller than the projection height of the LEDs  17  from the LED board  18 . With this configuration, light from the LEDs  17  is less likely to be blocked by the screw member  22  and uneven brightness is further less likely to occur. 
     The backlight unit  12  further includes the chassis  14  that holds the LED board  18  and the light guide plate  19 . The chassis  14  is the mount member to which the LED board  18  is mounted. With this configuration, the LED board  18  can be attached to the chassis  14  with the screw member  22 . 
     Second Embodiment 
     A second embodiment of this invention will be described with reference to  FIGS. 8 and 9 . In the second embodiment, arrangement of screw members  122  and arrangement of LEDs  117  are altered from ones in the first embodiment. The same structures, operations, and effects as those of the first embodiment will not be described. 
     As illustrated in  FIG. 8 , the screw members  122  according to this embodiment are arranged at end portions of an LED board  118 . Specifically, eight LEDs  117  are arranged in a line on the LED board  118  along a length direction (the X-axis direction) of the LED board  118 , and each of the screw members  122  is disposed between each of end-side LEDs  117  that are located closest to the ends of the LED board  118  in the length direction and a LED  117  adjacent to each end-side LED  117 . All of the LEDs  117  mounted on the LED board  118  are arrangement interval variation LEDs  124  that are arranged at intervals P 11  to P 14  that continuously and gradually vary. 
     Specifically, the arrangement interval variation LEDs  124  include two pairs of first LEDs  124   a  (four in total), two second LEDs  124   b , and two third LEDs  124   c . Each pair of the first LEDs  124   a  that are adjacent to each other is arranged so as to sandwich the screw member  122  in between. The second LEDs  124   b  are adjacent to the first LEDs  124   a  located close to a middle portion of the LED board  118 . The third LEDs  124   c  are arranged adjacent to the respective second LEDs  124   b . Among all of the LEDs  117 , the end-side LEDs  117  that are located closest to the ends of the LED board  118  and the LEDs  117  next to the respective end-side LEDs  117  are the first LEDs  124   a . Among all of the LEDs  117 , the third LEDs  124   c  are located closest to the middle portion of the LED board  118 . The second LEDs  124   b  are arranged closer to the middle portion of the LED board  118  next to the third LEDs  124   c . Herein, “P 11 ” denotes an interval between the pair of first LEDs  124   a , “P 12 ” denotes an interval between the first LED  124   a  and the second LED  124   b , P 13 ″ denotes an interval between the second LED  124   b  and the third LED  124   c , “P 14 ” denotes an interval between the pair of the third LEDs  124   c , and a size relation of the intervals satisfies an inequality of “P 11 &gt;P 12 &gt;P 13 &gt;P 14 ”. P 11  has a maximum value and P 14  has a minimum value. Specifically, a dimension of P 11  is about 5 mm, a dimension of P 12  is about 4 mm, a dimension of P 13  is about 3 mm, and a dimension of P 14  is about 2 mm. 
     All dots included in light reflection portions  123  of a light guide plate  119  are area variation dots  126 . The area variation dots  126  are patterned as illustrated in  FIGS. 8 and 9 . Specifically, an area ratio of the area variation dots  126  per unit area in a plane of a plate surface of the light guide plate  119  is the largest at end portions of the light guide plate  119  with respect to the X-axis direction (an arrangement direction of the LEDs  117 ). In other words, the area ratio of the area variation dots  126  is the largest at portions corresponding to the end-side first LEDs  124   a  among the arrangement interval variation LEDs  124  with respect to the X-axis direction. The area ratio gradually decreases as a distance from each end portion of the light guide plate  119  to a middle portion of the light guide plate  119  in the X-axis direction decreases, and the area ratio has a minimum value in the middle portion of the light guide plate  119 . In other words, the area ratio of the area variation dots  126  per unit area in the plane of the plate surface of the light guide plate  119  peaks at the end portions of the light guide plate  119  in the long-side direction (the X-axis direction), and the area ratio continuously and gradually decreases as the distance therefrom to the middle portion of the light guide plate  119  decreases. In this configuration, rays of light from the arrangement interval variation LEDs  124  enter the light guide plate  119  through a light entrance surface  119   b . The rays of light are reflected by the area variation dots  126  that are arranged so as to correspond to the intervals P 11  to P 14 . As a result, the exiting rays of light are equalized at the plane of the light guide plate  119 . The LED board  118  in this embodiment is made of metal or ceramic having a coefficient of thermal expansion lower than that of synthetic resin material. Accordingly, an expansion or contraction amount due to thermal expansion or thermal contraction is small, and thus deformation such as warping or deflection is less likely to occur even if the end portions of the LED board  118  are fixed with the screw members  122 . 
     Third Embodiment 
     A third embodiment of this invention will be described with reference to  FIGS. 10 and 11 . In the third embodiment, arrangement of screw members  222  and arrangement of LEDs  217  are changed from those of the second embodiment. The same structures, operations, and effects as those of the second embodiment will not be described. 
     As illustrated in  FIG. 10 , the screw members  222  according to this embodiment are arranged in intermediate portions of an LED board  218  between the end portions and a middle portion of the LED board  218 . Specifically, a total of fourteen LEDs  217  are arranged in a line on the LED board  218  along a length direction (the X-axis direction) of the LED board  218 . Each of the screw members  222  is arranged between the fourth LED  217  from an end of the LED board  218  in the length direction and the adjacent LED  217  on a middle side of the fourth LED  217 . 
     All the LEDs  217  are arrangement interval variation LEDs  224 . The arrangement interval variation LEDs  224  include two pairs of first LEDs  224   a  (four in total), two pairs of second LEDs  224   b  (four in total), two pairs of third LEDs  224   c  (four in total), and a pair of fourth LEDs  224   d . Each pair of the first LEDs  224   a  is arranged so as to sandwich a screw member  222  in between. Each pair of the second LEDs  224   b  is adjacent to the first LEDs  224   a  in each pair. Each pair of the third LEDs  224   c  is adjacent to the second LEDs  224   b  in each pair. Each of the fourth LEDs  224   d  is adjacent to one of third LEDs  224   c  on an outer side. The third LEDs  224   c  on an inner side are located closest to the middle portion of the LED board  218 . The fourth LEDs  224   d  are located closest to the ends of the LED board  218 . Herein, when “P 21 ” denotes an interval between the first LEDs  224   a , “P 22 ” denotes an interval between the second LED  224   a  and the second LED  224   b , “P 23 ” denotes an interval between the second LED  224   b  and the third LED  224   c , and “P 24 ” denotes an interval between the third LEDs  224   c  adjacent to each other and an interval between the third LED  224   c  and the forth LED  224   d , a size relation of the intervals satisfies an inequality of “P 21 &gt;P 22 &gt;P 23 &gt;P 24 ”. P 21  has a maximum value and P 24  has a minimum value. Specifically, a dimension of P 21  is about 5 mm, a dimension of P 22  is about 4 mm, a dimension of P 23  is about 3 mm, and a dimension of P 24  is about 2 mm. 
     As illustrated in  FIGS. 10 and 11 , light reflection portions  223  of a light guide plate  219  include area variation dots  226 . The area variation dots  226  are pattered as follows. An area ratio of the area variation dots  226  per unit area in a plane of a plate surface of the light guide plate  219  is the smallest in three portions including both end portions and a middle portion of the light guide plate  219  with respect to the X-axis direction (an arrangement direction of the LEDs  217 ). The area ratio of the area variation dots  226  gradually decreases as a distance from each of the three portions increases, and the area ratio is the largest in a portion corresponding to the screw member  222  with respect to the X-axis direction. In this configuration, rays of light from the arrangement interval variation LEDs  224  enter the light guide plate  219  through a light entrance surface  219   b , and the rays of light are reflected by the area variation dots  226  that are arranged so as to correspond to the intervals P 21  to P 24 . As a result, the exiting rays of light are equalized in the plane of the light guide plate  219 . 
     Fourth Embodiment 
     A fourth embodiment of this invention will be described with reference to  FIGS. 12 and 13 . In the fourth embodiment, a pair of LED boards  318  is arranged. The same structures, operations, and effects as those of the first embodiment will not be described. 
     As illustrated in  FIG. 12 , the LED boards  318  of this embodiment are arranged in long-side end portions of a chassis  314 . The LED boards  318  are arranged so as to sandwich a light guide plate  319  from both sides of the light guide plate  319  with respect to a short-side direction (the Y-axis direction) of the light guide plate  319 . The LED boards  318  are attached to long-side plates  314   b  of the chassis  314  with screw members  322 . Among outer peripheral end surfaces of the light guide plate  319 , long-side end surfaces of the light guide plate  319  are light entrances  319   b . Light reflection portions  323  of the light guide plate  319  are pattered as illustrated in  FIGS. 12 and 13 . Specifically, an area ratio of the light reflection portion  323  per unit area in a plane of a plate surface of the light guide plate  319  is the smallest in end portions of the light guide plate  319  with respect to the Y-axis direction (an arrangement direction between the LEDs  317  and the light guide plate  319 ), and gradually increases as a distance from the end portion increases, and the area ratio is the largest in a middle portion of the light guide plate  319 . The area ratio of the light reflection portion  232  in the X-axis direction varies similar to the first embodiment. Accordingly, among dots of the light reflection portions  323 , dots arranged in the middle portion of the light guide plate  319  in the X and Y directions have the largest area ratio, and dots arranged at four corners of the light guide plate  319  have the smallest area ratio. 
     Fifth Embodiment 
     A fifth embodiment of this invention will be described with reference to  FIGS. 14 and 15 . In the fifth embodiment, arrangement of LED boards  418  is altered from one in the first embodiment. The same structures, operations, and effects as those of the first embodiment will not be described. 
     As illustrated in  FIG. 14 , the LED boards  418  according to this embodiment are arranged in short-side end portions of a chassis  414  so as to sandwich a light guide plate  419  from sides of the light guide plate  419  with respect to a long-side direction (the X-axis direction) of the light guide plate  419 . Among outer peripheral end surfaces of the light guide plate  419 , short-side end surfaces thereof are light entrance surfaces  419   b . Each LED board  18  is attached to a short-side plate  414   b  of the chassis  414  with a single screw member  422 . The screw member  422  is located close to one (an upper side in  FIG. 14 ) of end portions of the LED board  418  with respect to a length direction (the Y-axis direction) of the LED board  418 . 
     As illustrated in  FIG. 14 , LEDs  417  mounted on the LED boards  418  include arrangement interval variation LEDs  424 . The arrangement interval variation LEDs  424  in each LED board  418  include a pair of first LEDs  424   a , a second LED  424   b , and a third LED  424   c . The first LEDs  424   a  are arranged adjacent to each other with the screw member  422  in between. The second LED  424   b  is adjacent to one of the first LEDs  424   a  that is on a middle side (a side opposite to the screw member  422 ) of the LED board  418 . The third LED  424   c  is adjacent to the second LED  424   b . Herein, when “P 41 ” denotes an interval between the pair of the first LEDs  424   a , “P 42 ” denotes an interval between the first LED  424   a  and the second LED  424   b , and “P 43 ” denotes an interval between the second LED  424   b  and the third LED  424   c , a size relation of the intervals satisfies “P 41 &gt;P 42 &gt;P 43 ”. P 41  has a maximum value and the P 43  has a minimum value. Specifically, a dimension of P 41  is about 5 mm, a dimension of P 42  is about 4 mm, and a dimension of P 43  is about 3 mm. 
     As illustrated in  FIG. 14 , the LEDs  417  include arrangement interval constant LEDs  425  in addition to the arrangement interval variation LEDs  424 . The arrangement interval constant LEDs  425  in each LED board  418  include a fourth LED  425   a , a fifth LED  425   b , and a sixth LED  425   c . The fourth LED  425   a  is adjacent to the third LED  424   c , which is one of the arrangement interval variation LEDs  424 , on an opposite side of the third LED  424   c  from the second LED  424   b . The fifth LED  425   b  is adjacent to the fourth LED  425   a . The sixth LED  425   c  is adjacent to the fifth LED  425   b . The sixth LED  425   c  is located in an opposite end portion of the LED board  418  from a screw member  422  side. Herein, when “P 44 ” denotes an interval between the third LED  424   c  and the fourth LED  425   a , “P 45 ” denotes an interval between the fourth LED  425   a  and the fifth LED  425   b , and “P 46 ” denotes an interval between the fifth LED  425   b  and the sixth LED  425   c , a relation of the intervals satisfies an equality of “P 44 =P 45 =P 46 ” and an inequality of “P 43 &gt;P 44 =P 45 =P 46 ”. Specifically, a dimension of P 4 , a dimension of P 5 , and a dimension of P 6  are about 2 mm and substantially the same. As is just described, the arrangement interval variation LEDs  424  and the arrangement interval constant LEDs  425  are arranged in asymmetrical with respect to a symmetrical line that passes through a middle of the LED board  418  in the length direction. 
     Dots included in light reflection portions  423  of the light guide plate  419  include area variation dots  426  and area constant dots  427 . The area variation dots  426  are patterned as illustrated in  FIGS. 14 and 15 . An area ratio per unit area in a plane of a plate surface of the light guide plate  419  is the largest in an upper end portion of the light guide plate  419  in  FIG. 14  with respect to the Y-axis direction (an arrangement direction of the LEDs  417 ). In other words, the area ratio is the largest at a portion corresponding to the first LEDs  424   a  that are located closest to the end among the arrangement interval variation LEDs  424  with respect to the Y-axis direction. The area ratio gradually decreases toward a lower side in  FIG. 14  along the Y-axis direction. An arrangement region  426 A where the area variation dots  426  are arranged substantially corresponds to an arrangement region where the arrangement interval variation LEDs  424  are arranged. The area constant dots  427  are arranged in a lower portion of the light guide plate  419  in  FIG. 14  with respect to the Y-axis direction. The area constant dots  427  are patterned such that an area ratio per unit area in the plane of the plate surface of the light guide plate  419  are substantially constant regardless of positions with respect to the Y-axis direction. An arrangement region  427 A where the area constant dots  427  are arranged corresponds to an arrangement region where the arrangement interval constant LEDs  425  are arranged. The area variation dots  426  and the area constant dots  427  included in the light reflection portions  423  are arranged in asymmetrical with respect to a symmetrical line that passes through a middle of the light guide plate  419  with respect to the short-side direction of the light guide plate  419 . 
     Sixth Embodiment 
     A sixth embodiment of this invention will be described with reference to  FIG. 16 . In the sixth embodiment, an LED board  518  is attached to a chassis  514  with a clip member  28 . The same structures, operations, and effects as those of the first embodiment will not be described. 
     As illustrated in  FIG. 16 , the LED board  518  according to this embodiment is attached to a side-plate  514   b  of the chassis  514  with the clip member (the board attachment member)  28  that is made of synthetic resin. The clip member  28  includes a base portion  28   a , a shaft portion  28   b , and a pair of stopper portions  28   c . The base portion  28   a  contacts a mount surface  518   a  of the LED board  518 . The shaft portion  28   b  projects from the base portion  28   a  so as to penetrate an insertion hole  518   b  of the LED board  518  and an attachment hole  514   b   1  of the side-plate  514   b . The stoppers  28   c  extend from a projected end of the shaft portion  28   b  toward the base portions  28   a . The stoppers  28   c  stop at a peripheral portion of the attachment hole  514   b   1  of the side-plate  514   b . The stopper portions  28   c  elastically deform with respect to the shaft portion  28   b . Specifically, the stopper portions  28   c  can elastically deform so as to approach the shaft portion  28   b . Accordingly, the stopper portions  28   c  can pass through the insertion hole  518   b  and the attachment portion  514   b   1 . The LED board  518  is held between the side-plate  514   b  of the chassis  514  and the base portion  28   a  of the clip member  28 . 
     Seventh Embodiment 
     A seventh embodiment of the technology will be described with reference to  FIGS. 17 to 19 . According to the seventh embodiment, a television device TV does not include a cabinet. The same configurations, functions, and effects as those in the first embodiment will not be described. 
     As illustrated in  FIG. 17 , the television device TV according to this embodiment includes a liquid crystal display unit (a display unit) LDU, circuit boards PWB, MB, and CTB, a cover CV, and a stand ST. The circuit boards PWB, MB, and CTB are attached to the rear surface (the back surface) of the liquid crystal display unit LDU. The cover CV is attached to the rear surface of the liquid crystal display unit LDU so as to cover the circuit boards PWB, MB, and CTB. The liquid crystal display unit LDU is supported by the stand ST with a display surface thereof held along the vertical direction (the Y-axis direction). A liquid crystal display device  610  in this embodiment is a part of the above-described television device TV at least other than a part configured to receive television signals (e.g., a tuner section of a main circuit board MB). As illustrated in  FIG. 18 , the liquid crystal display unit LDU has a landscape rectangular overall shape (an elongated shape). The liquid crystal display unit LDU includes a liquid crystal panel  611  and a backlight unit  612  collectively held by a bezel  613  and a chassis  614 , which are components of the liquid crystal display device  610  to form an exterior of the liquid crystal display device  610 . The chassis  614  in this embodiment is one of the components to form the exterior and a part of the backlight  612 . 
     As illustrated in  FIGS. 18 and 19 , the liquid crystal display unit LDU of the liquid crystal display device  610  is arranged in a space between the bezel (a front frame)  613  that forms a front exterior and the chassis (a rear chassis)  614  that forms a rear exterior. Major components arranged between the bezel  613  and the chassis  614  include at least the liquid crystal panel  611 , optical members  615 , a light guide plate  619 , and LED units (light source units) LU. The liquid crystal panel  611 , the optical members  615 , and the light guide plate  619  are layered directly onto each other and sandwiched between the bezel  613  on the front and the chassis  614  on the rear. The liquid crystal display device  610  in this embodiment does not include the frame  16  of the first embodiment arranged between the liquid crystal panel  11  and the optical member  15  (see  FIGS. 2 and 3 ). 
     As illustrated in  FIGS. 18 and 19 , the backlight unit  612  includes the optical members  615 , the light guide plate  619 , the LED units LU, and the chassis  614 , that is, apart of the liquid crystal display unit LDU other than the liquid crystal panel  611  and the bezel  613 . The LED units LU included in the backlight unit  612  are arranged adjacent to the light guide plate  619  on a front side in  FIG. 18  (a left side in  FIG. 19 ) between the bezel  613  and the chassis  614 , and arranged in a line along the X-axis direction. Each LED unit LU includes LEDs  617 , an LED board  618  on which the LEDs  617  are mounted, and a heat dissipation member (a heat spreader, a mount base member)  29 . The LED board  618  is attached to the heat dissipation member  29  by attaching a screw member  622  at a middle portion of the LED board  618  with respect to the length direction of the LED board  618 . 
     Eighth Embodiment 
     An eighth embodiment of this invention will be described with reference to  FIG. 20 . The eighth embodiment is a modification of the fourth embodiment. Arrangement of screw members  722 A,  722 B and arrangement of LEDs  717 A,  717 B in LED boards  718 ,  718 B are different from ones of the above embodiment. The same structures, operations, and effects as those of the first embodiment will not be described. 
     As illustrated in  FIG. 20 , the LED boards  718 A,  718 B according to this embodiment are arranged so as to sandwich a light guide plate  719  from both sides of the light guide plate  719  with respect to its short-side direction (the Y-axis direction). One of the LED boards  718 A and  718 B that is on a lower side in  FIG. 20  includes a screw member  722 A and LEDs  717 A. Arrangement of the screw member  722 A and arrangement of the LEDs  717 A are similar to those in the first embodiment. The other one of the LED boards  718 A and  718 B that is on an upper side in  FIG. 20  includes screw members  722 B and LEDs  717 B. Arrangement of the screw member  722 B and arrangement of the LEDs  722 B are similar to those in the second embodiment. Specifically, on the LED board  718 B arranged on the lower side in  FIG. 20 , one screw member  722 A is attached at a substantially middle portion thereof with respect to the length direction. The LEDs  717 A mounted on the LED board  718 A include arrangement interval variation LEDs  724 A and arrangement interval constant LEDs (arrangement interval constant light sources)  725 A. The arrangement interval variation LEDs  724 A are arranged at intervals P 1  to P 3  that decrease as a distance from the screw member  722 A increases. The arrangement interval constant LEDs  725 A are arranged at intervals P 4  and P 5  that are substantially constant regardless of the distance from the screw member  722 A. Configurations of the intervals P 1  to P 5  between the LEDs  717 A are the same as those in the first embodiment. On the other hand, on the LED board  718 B arranged on the upper side in  FIG. 20 , two screw members  722 B are attached to end portions thereof with respect to the length direction. All the LEDs  717 B mounted on the LED board  718 B are arrangement interval variation LEDs  724 B that are arranged at intervals P 11  to P 14  decreasing as a distance from each screw member  722 B increases. Configurations of the intervals P 11  to P 14  between the LEDs  717 B are the same as those described in the second embodiment. On the LED boards  718 A and  718 B according to this embodiment, the arrangement of the LEDs  717 A and  717 B and the arrangement of the screw member  722 A and  722 B are asymmetric in an up-and-down direction in  FIG. 20 . 
     Corresponding to the arrangement of the LEDs  717 A and  717 B, light reflection portions  723  that are configured to direct more light to an outside of the light guide plate  719  have following configurations. The light guide plate  719  are divided into a first region A 1  on a lower side of  FIG. 20  and a second region A 2  on an upper side of  FIG. 20  along a long-side direction of the light guide plate  719 . The light reflection portions  723  have different area distribution in the first region A 1  and the second region A 2 . Specifically, in the first region A 1 , dots of the light reflection portions  723  includes area variation dots  726 A and area constant dots  727 A. An area distribution of the area variation dots  726 A in a plane of a plate surface of the light guide plate  719  becomes smaller as a distance from the screw member  722 A increases along the X-axis direction (an arrangement direction of the LEDs  717 ). An area distribution of the area constant dots  727 A in the plane of the plate surface of the light guide plate  719  is constant regardless of the distance from the screw member  722 A in the X-axis direction. Specific arrangement of the area variation dots  726 A and the area constant dots  727 A in the first region A 1  is the same as those described in the first embodiment. On the other hand, in the second region A 2 , dots included in the light reflection portions  723  only include area variation dots  726 B. In an area distribution of the area variation dots  726 B in the plane of the plate surface of the light guide plate, areas of the area variation dots  726 B decrease as a distance from each screw member  722 B increases along the X-axis direction. Specific arrangement of the area variation dots  726 B in the second region A 2  is the same as those described in the second embodiment. Even in such a configuration, light emitted from the LED  717 A and  717 B of the respective LED boards  718 A and  718 B and entering the light guide plate  719  is reflected by the light reflection portions  723  having a dot pattern corresponding to the arrangement of the LEDs  717 A and  717 B. Thus, the amount of light exiting the light guide plate  719  is equalized in the plane. 
     Ninth Embodiment 
     A ninth embodiment of this invention will be described with reference to  FIG. 21 . In the ninth embodiment, a screw member  822  is different from one in the first embodiment. The same structures, operations, and effects as those of the first embodiment will not be described. 
     As illustrated in  FIG. 21 , the screw member  822  according to this embodiment has a projection height (a thickness dimension of a head portion  822   b ) measured from a mount surface  818   a  of an LED board  818  that is greater than a projection height (a distance from the mount surface  818   a  to a main light-emitting surface  817   a ) of an LED  817  measured from the mount surface  818   a  of an LED board  818 . In other words, the head portion  822   b  of the screw member  822  is located between the main light-emitting surface  817   a  of the LED  817  and a light entrance surface  819   b  of the light guide plate  819  with respect to the Y-axis direction (an arrangement direction between the LED  817  and the light guide plate  819 ). If an environmental temperature inside a chassis  814  increases and the light guide plate  819  expands due to thermal expansion, the light entrance surface  819   b  of the light guide plate  819  may displace closer to the LED  817  along the Y-axis direction. In such a case, the head portion  822   b  of the screw member  822  comes into contact with the light entrance surface  819   b  and restricts further displacement of the light entrance surface  819   b  toward the LED  817 . With this configuration, the light entrance surface  819   b  of the light guide plate  819  is less likely to contact the LED  817  and thus the LED  817  is less likely to be damaged or broken. In  FIG. 21 , a thermally expanded light guide plate  819  is indicated by a double chain line. 
     Other Embodiments 
     The technology is not limited to the above embodiments described in the above description and the drawings. For example, the following embodiments may be included in technical scopes of the technology. 
     (1) In the first and fifth embodiments, the LEDs include the arrangement interval variation LEDs and the arrangement interval constant LEDs. However, all of the LEDs included in the LED boards of the first and fifth embodiment may be the arrangement interval variation LEDs. 
     (2) In the second to fourth embodiments, all LEDs are arrangement interval variation LEDs. However, the LEDs on the LED boards of the second to fourth embodiments may include the arrangement interval variation LEDs and the arrangement interval constant LEDs. 
     (3) In addition to the above embodiments, the specific number the arrangement interval variation LEDs on the LED or the interval between the arrangement interval variation LEDs may be altered as appropriate. In similar, the specific number of the arrangement interval constant LEDs or the interval between the arrangement interval distant LEDs altered as appropriate. 
     (4) In the first and fourth embodiments, the screw member  22  is arranged in the middle portion of the LED board with respect to the long-side direction. However, the screw member may be at a position off (shifted) from the middle of the LED board in each of the first and fourth embodiments. In such a case, the arrangement of the arrangement interval variation LEDs or the arrangement of the arrangement interval variation LEDs may be altered as appropriate according to the arrangement of the screw member. 
     (5) In the second, third, and fifth embodiments, the screw members are located off from the middle portion of the LED board with respect to the long-side direction. However, the screw members may be located in the middle portion of the respective LED boards in the second, third, and fifth embodiments. In such a case, the arrangement of the arrangement interval variation LEDs or the arrangement of the arrangement interval variation LEDs may be altered as appropriate according to the arrangement of the screw member. 
     (6) In addition to the above embodiments, the arrangement of the screw member or the clip member for attaching the LED board to the chassis may be altered as appropriate. 
     (7) In the first to fifth and seventh embodiments, the screw member may be replaced with the clip member included in the seventh embodiment. 
     (8) In the above embodiments, one or two of the screw members or the clip members are attached to the LED board. However, three or more screw members or clip members may be attached to the LED board. 
     (9) In the above embodiments, the arrangement region of the area variation dots that are included in the light reflection portions of the light guide plate substantially overlaps the arrangement region of the arrangement interval variation LEDs. However, large parts of the respective arrangement regions may overlap each other while other parts thereof may not overlap, or some parts of the respective arrangement regions may overlap each other while large parts thereof may not overlap. 
     (10) In the above embodiments, the arrangement region of the area constant dots that are included in the light reflection portions of the light guide plate substantially overlaps the arrangement region of the arrangement interval constant LEDs. However, large parts of the respective arrangement regions may overlap each other while other parts thereof may not overlap, or some parts of the respective arrangement regions may overlap each other while large parts thereof may not overlap. 
     (11) In the second and third embodiments, a pair of the LED boards may be arranged at the respective long-side end portions of the chassis such as those in the fourth embodiment, or the LED boards may be arranged at the respective short-side end portions of the chassis such as those in the fifth embodiment. 
     (12) In the first to fourth embodiments, as is described in the fifth embodiment, the screw member may be arranged in an eccentric portion of the LED board. Further, the arrangement interval variation LEDs and the arrangement interval constant LEDs may be arranged in asymmetrical. Furthermore, the area variation dots and the area constant dots may be arranged in asymmetrical. 
     (13) In addition to the above embodiments, the specific variation levels of the intervals between the LEDs may be altered as appropriate. 
     (14) In the first to sixth embodiments, the LED board may be attached to a heat dissipation member with the screw member or the clip member such as that described in the seventh embodiment. 
     (15) In addition to the above embodiments, the specific variation levels of the area ratio of the light reflection portions may be altered as appropriate. 
     (16) In the above embodiments, the screw member and the clip member are used as attaching members to attach the LED board to the chassis. However, in addition to the above members, a rivet member may be used. 
     (17) In the first to third, sixth, and seventh embodiments, the LED board is arranged on one of the long-side end portions of the chassis. However, the LED board may be arranged on only one of short-side end portions of the chassis. 
     (18) In the above embodiment, the one LED board is arranged opposite the one end portion of the light guide plate or a pair of the LEDs are arranged opposite the end portions of the light guide plate. However, the LED boards may be arranged opposite the three end portions or all of the four end portions of the light guide plate. 
     (19) In the above embodiments, one or two LED boards are arranged on one side of the light guide plate. However, three or more LED boards may be arranged on one side of the light guide plate. 
     (20) In the above embodiments, the color portions of the color filtered in the liquid crystal panel are in three colors of R, G, and B. However, the color portions may be provided in four or more colors. 
     (21) In the above embodiments, the LEDs are used as light sources. However, other types of light sources such as organic ELs may be used. 
     (22) In the above embodiments, the TFTs are used as switching components of the liquid crystal display device. A liquid crystal display device including switching components other than TFTs (e.g., thin film diodes (TFDs)) may be included in the scope of the technology. A black-and-white liquid crystal display device other than the color liquid crystal display device may be included in the scope of the technology. 
     (23) In the above embodiments, the liquid crystal display device including the liquid crystal panel as a display panel is used. However, a display device including other type of display panel may be included in the scope of the technology. 
     (24) In the above embodiments, the television device including the tuner is used. However, a display device including other type of display panel may be included in the scope of the technology. Specifically, liquid crystal display devices used for digital signage or electric blackboards may be included in the scope of the technology. 
     (25) In the eighth embodiment, the LED board (or LEDs), the screw member, and the light reflection portion included in the first embodiment and the LED board (or LEDs), the screw member, and the light reflection portion included in the second embodiment are used in combination. However, the LED board (or LEDs), the screw member, and the light reflection portion included in the third embodiment may be combined. Further, the configuration of the eighth embodiment may be applied to the fifth embodiment in which the LED boards are arranged at the respective short-side end portions of the chassis. 
     (26) In the ninth embodiment, the screw member is located between the main light-emitting surface of the LED and the light entrance surface of the light guide plate. However, the surface of the head portion opposite the light entrance surface may be altered as appropriate. The surface of the head portion opposite to the light entrance surface may be on the same plane with the main light-emitting surface of the LED or on the same plane with the light entrance surface. Further, similar to the ninth embodiment, a surface of the clip member opposite to the light entrance surface in the sixth embodiment may be located between the main light-emitting surface of the LED and the light entrance surface of the light guide plate, or may be on the same plane with the main light-emitting surface of the LED or on the same plane with the light entrance surface. 
     EXPLANATION OF SYMBOLS 
       10 ,  610 : liquid crystal display device (display device),  11 ,  611 : liquid crystal panel (display panel),  12 ,  612 , backlight unit (lighting device),  14 ,  414 ,  514 ,  814 : chassis (mount member),  17 ,  117 ,  217 ,  317 ,  417 ,  617 ,  717 A,  717 B,  817 : LED (light source),  18 ,  118 ,  218 ,  318 ,  418 ,  518 ,  618 ,  718 A,  718 B,  818 : LED board (light source board),  19 ,  119 ,  219 ,  319 ,  419 ,  619 ,  719 ,  819 : light guide plate,  19   a : light exit surface (plate surface),  19   b ,  219   b ,  319   b ,  419   b ,  819   b : light entrance surface (end surface, light source opposed surface),  19   d : LED non-opposed end surface (light source non-opposed end surface),  22 ,  122 ,  222 ,  322 ,  422 ,  622 ,  722 A,  722 B,  822 : screw member (board attachment member),  23 ,  123 ,  223 ,  323 ,  423 ,  723 : light reflection portion,  24 ,  124 ,  224 ,  424 ,  724 A,  724 B: arrangement interval variation LED (arrangement interval variation light source),  25 ,  425 ,  725 A: arrangement interval constant LED (arrangement interval constant light source), P 1  to P 3 , P 11  to P 14 , P 21  to P 24 , P 41  to P 43 : interval, P 4 , P 5 , P 44  to P 46 : interval,  28 : clip member (board attachment member),  29 : heat dissipation member (mount member), TV: television device.