Abstract:
Provided are a light source device which is capable of constantly maintaining an interval between the light source and the light guide plate when the light guide plate is thermally expanded by a simpler configuration without adding a separate component, while suppressing the manufacturing costs, and a display apparatus. The light source device includes a light guide plate for emitting light made incident on one side surface from one surface thereof, a light source disposed on the one side surface side of the light guide plate, and a rear housing body for housing the light guide plate and the light source, wherein a heat spreader, which holds the light guide plate and the light source and transfers heat emitted from the light source to a bottom surface of the rear housing body, is configured to slide on the bottom surface of the rear housing body, such that the light source which is held together with the light guide plate by the heat spreader also slides according to an expansion and contraction of the light guide plate.

Description:
[0001]    This application is the national phase under 35 U.S.C. §371 of PCT International Application No. PCT/JP2013/067934 which has an International filing date of Jun. 28, 2013 and designated the United States of America. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to a light source device which includes a light guide plate for emitting light made incident on one side surface from one surface thereof, a light source disposed on the one side surface side of the light guide plate, and a housing body for housing the light guide plate and the light source, and a display apparatus including the light source device. 
       DESCRIPTION OF RELATED ART 
       [0003]    In the case of a so-called edge light type light source device which irradiates a liquid crystal panel with light from a side surface side thereof, the liquid crystal panel includes, on a rear side thereof, a light guide plate which guides light from a light source to the liquid crystal panel. 
         [0004]    However, recently, a size of the liquid crystal display apparatus is becoming larger, and thereby the size of the light guide plate included in the liquid crystal display apparatus has also been increased. In this way, due to the size of the light guide plate becoming larger, a thermal expansion amount of the light guide plate caused by heat generated during operating the liquid crystal display apparatus is also increased. 
         [0005]    Therefore, in the edge light type liquid crystal display apparatus, it is necessary to sufficiently secure an interval between a side surface of the light guide plate, that is, a so-called incident surface and the light source. 
         [0006]    However, when the interval between the light source and the incident surface is wide, an incident amount to the incident surface is decreased, and luminance may be deteriorated. 
         [0007]    For the above-described problem, International Publication Pamphlet No. 2009/122604 discloses a planar light source device which is provided with a holding body for connecting a light guide plate and a light source unit while maintaining an interval therebetween, wherein the light source unit is configured so as to move in response to an expansion and contraction of the light guide body, such that the interval between the light source unit and the side surface of the light guide body with respect to the expansion and contraction of the light guide body is constantly maintained by the holding body. 
       SUMMARY 
       [0008]    However, in such an above-described planar light source device of International Publication Pamphlet No. 2009/122604, the holding body for connecting the light guide body and the light source unit is separately provided, and thereby, a configuration of the planar light source device is complicated, and the number of components is increased, which causes an increase in manufacturing costs. 
         [0009]    In consideration of the above-mentioned circumstances, it is an object of the present invention to provide a light source device which includes a light guide plate configured to emit light made incident on one side surface from one surface thereof, a light source disposed on the one side surface side of the light guide plate, and a housing body configured to house the light guide plate and the light source, wherein a heat transfer unit, which holds the light guide plate and the light source and transfers heat emitted from the light source to one surface of the housing body, is slidably formed on the one surface of the housing body, such that the light source which is held together with the light guide plate by the heat transfer unit also slides according to an expansion and contraction of the light guide plate, and thereby it is possible to constantly maintain an interval between the light source and the light guide plate when the light guide plate is thermally expanded by a simpler configuration without adding a separate component, while suppressing the manufacturing costs, and a display apparatus including the light source device. 
         [0010]    The light source device according to the present invention is a light source device including a light guide plate configured to emit light made incident on one side surface from one surface thereof, a light source disposed on the one side surface side of the light guide plate, and a housing body configured to house the light guide plate and the light source, the light source device comprising: a heat transfer unit configured to hold the light guide plate and the light source and transfer heat emitted from the light source to one surface of the housing body, wherein the heat transfer unit has a plate part which is interposed between the other surface of the light guide plate and the one surface of the housing body, the heat transfer unit is configured to slide on the one surface of the housing body in a facing direction in which the one side surface of the light guide plate and the other side surface corresponding thereto face each other, and the heat transfer unit is configured to be prevented from being separated from the one surface of the housing body. 
         [0011]    According to the present invention, since the light source is held together with the light guide plate by the heat transfer unit, for example, when the light guide plate is thermally extended, and contracted, the heat transfer unit slides on the one surface of the housing body in the direction in which the one side surface and the other side surface of the light guide plate face each other according to the expansion and contraction of the light guide plate, without being separated from the one surface of the housing body. Thereby, since the light source also moves, when the light guide plate is thermally expanded, the interval between the light source and the light guide plate is constantly maintained. 
         [0012]    The light source device according to the present invention is a light source device including a light guide plate configured to emit light made incident on one side surface from one surface thereof, a light source disposed on the one side surface side of the light guide plate, and a housing body configured to house the light guide plate and the light source, the light source device comprising: a heat transfer unit configured to hold the light guide plate and the light source and transfer heat emitted from the light source to one surface of the housing body, wherein the heat transfer unit includes an engaging part configured to be engaged to the light guide plate, the light guide plate includes an engaged part to which the engaging part is engaged, and the heat transfer unit is configured so as to slide on the one surface of the housing body according to an expansion and contraction of the light guide plate. 
         [0013]    According to the present invention, since the heat transfer unit and the light guide plate are engaged with each other by the engaging part of the heat transfer unit and the engaged part of the light guide plate, for example, when the light guide plate is thermally expanded, and contracted in the facing direction, the heat transfer unit slides according to the expansion and contraction of the light guide plate, and thereby, the light source also moves while the interval between the light source and the light guide plate is constantly maintained. 
         [0014]    The light source device according to the present invention is a light source device, wherein the heat transfer unit includes a long hole formed in the plate part with the facing direction as a major axis direction, and an engaging pin which is inserted into the long hole of the plate part, and has one end which is fixed to the one surface of the housing body and the other end which is provided with a head portion having a larger diameter than a minor axis of the long hole. 
         [0015]    According to the present invention, the heat transfer unit slides in the major axis direction of the long hole, that is, in the facing direction, while separating from the one surface of the housing body is prevented by the engaging pin. 
         [0016]    The light source device according to the present invention is a light source device, wherein the heat transfer unit is adhered to the light guide plate by the plate part, and the heat transfer unit is configured so as to slide according to the expansion and contraction of the light guide plate in the facing direction. 
         [0017]    According to the present invention, since the plate part of the heat transfer unit is adhered to the light guide plate, for example, when the light guide plate is thermally expanded, and contracted in the facing direction, the heat transfer unit slides according to the expansion and contraction of the light guide plate, and thereby, the light source also moves while the interval between the light source and the light guide plate is constantly maintained. 
         [0018]    The light source device according to the present invention is a light source device, wherein the light source is further provided on the other side surface side of the light guide plate, and comprising: an abutting part configured to abut the one side surface or the other side surface of the light guide plate, and maintain an interval between the one side surface or the other side surface and the light source, and a spring configured to pull the plate part to a side opposite to a direction in which the light guide plate is extended. 
         [0019]    According to the present invention, when the light guide plate is extended (thermally expanded) in the facing direction, the abutting part and the one side surface or the other side surface of the light guide plate abut each other, and in this state, the light guide plate is continuously expanded. In addition, when the light guide plate is contracted, with the abutting part and the one side surface or the other side surface of the light guide plate abutting each other, the plate part is pulled to the side opposite to the direction in which the light guide plate is extended by the spring. Accordingly, the light source also moves according to the expansion and contraction of the light guide plate while the interval between the same and the light guide plate is constantly maintained. 
         [0020]    The light source device according to the present invention is a light source device, comprising: a substrate on which the light source is mounted on one surface thereof, wherein the substrate is provided with an abutting part which is formed on the one surface of the substrate to abut the one side surface or the other side surface of the light guide plate, and maintain an interval between the one side surface or the other side surface and the light source, the heat transfer unit includes a support plate which is extended at an edge of the plate part so that one surface thereof abuts the other surface of the substrate, and the one surface of the substrate faces the one side surface or the other side surface of the light guide plate, and the support plate includes a pressing spring which is disposed on the other surface side of the support plate to press the plate part to the side opposite to the direction in which the light guide plate is extended. 
         [0021]    According to the present invention, the plate part is always pressed to the side opposite to the direction in which the light guide plate is extended by the spring. When the light guide plate is extended (thermally expanded) in the facing direction, the abutting part and the one side surface or the other side surface of the light guide plate abut each other, and in this state, the light guide plate is continuously expanded. In addition, when the light guide plate is contracted, with the abutting part and the one side surface or the other side surface of the light guide plate abutting each other, the plate part is pressed to the side opposite to the direction in which the light guide plate is extended by the spring. Accordingly, the light source also moves according to the expansion and contraction of the light guide plate while the interval between the same and the light guide plate is constantly maintained. 
         [0022]    The display apparatus according to the present invention is a display apparatus comprising: the light source device defined above; and a display panel which is provided on the one surface side of the light guide plate of the light source device, and displays an image using light made incident thereon through the light guide plate. 
         [0023]    According to the present invention, the light made incident on the light guide plate of the light source device is propagated in the light guide plate while being totally reflected, and the light is uniformly emitted from the one surface of the light guide plate, such that the image is displayed by the display panel using the light emitted from the light guide plate. 
         [0024]    According to the present invention, since a conventional heat transfer unit is used, it is possible to constantly maintain the interval between the light source and the light guide plate when the light guide plate is thermally expanded by a simpler configuration without adding a separate component, while suppressing the manufacturing costs. 
         [0025]    The above and further objects and features will move fully be apparent from the following detailed description with accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0026]      FIG. 1  is an exploded perspective view illustrating a configuration of main components of a liquid crystal display apparatus according to Embodiment 1 of the present invention. 
           [0027]      FIG. 2  is a transverse cross-sectional view illustrating the configuration of the main components of the liquid crystal display apparatus according to Embodiment 1 of the present invention while a part thereof is not illustrated. 
           [0028]      FIG. 3  is an explanatory view describing holding of a heat spreader in the liquid crystal display apparatus according to Embodiment 1 of the present invention. 
           [0029]      FIG. 4  is a partial cross-sectional view illustrating a cross-section taken on line A-A of  FIG. 3 . 
           [0030]      FIG. 5  is a partial cross-sectional view describing a relation between the heat spreader and a light guide plate in a liquid crystal display apparatus according to Embodiment 2 of the present invention. 
           [0031]      FIG. 6  is a partial cross-sectional view describing a relation between the heat spreader and the light guide plate in a liquid crystal display apparatus according to Embodiment 3 of the present invention. 
           [0032]      FIG. 7  is a partial cross-sectional view illustrating a cross-section taken on line B-B of  FIG. 6 . 
           [0033]      FIG. 8  is a partial cross-sectional view describing a relation between the heat spreader and the light guide plate in a liquid crystal display apparatus according to Embodiment 4 of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0034]    Hereinafter, a case in which a light source device and a display apparatus according to embodiments of the present invention are applied to a so-called liquid crystal display apparatus including a liquid crystal display panel will be described in detail, by way of an example, with reference to the accompanying drawings. Hereinafter, for the convenience of explanation, a left-right and an up-down of the liquid crystal display apparatus are referred to as a lateral direction and a longitudinal direction, respectively. 
       Embodiment 1 
       [0035]      FIG. 1  is an exploded perspective view illustrating a configuration of main components of a liquid crystal display apparatus according to Embodiment 1 of the present invention. A liquid crystal display apparatus  100  according to Embodiment 1 of the present invention is illustrated in  FIG. 1 . In addition,  FIG. 2  is a transverse cross-sectional view illustrating the configuration of the main components of the liquid crystal display apparatus  100  according to Embodiment 1 of the present invention while a part thereof is not illustrated. The liquid crystal display apparatus  100  according to Embodiment 1 of the present invention is a so-called edge light type, and has a light source at both ends thereof in the lateral direction. 
         [0036]    The liquid crystal display apparatus  100  includes a liquid crystal display panel  10 , a front housing body  20 , an optical sheet  30 , and a light source device  1 . In addition, the light source device  1  has a light guide plate  40 , light source units  50 , heat spreaders  60 , and a rear housing body  70  (housing body). 
         [0037]    The liquid crystal display apparatus  100  has a pair of light source units  50 , as described above. The light source units  50  are disposed inside of a housing of the liquid crystal display apparatus  100  formed by the front housing body  20  and the rear housing body  70 . One of the pair of light source units  50  is disposed on one end side of the liquid crystal display apparatus  100  in the lateral direction thereof, and the other one is disposed on the other end side in the lateral direction. 
         [0038]    The light source units  50  include light sources  51  such as a plurality of LEDs having emission wavelengths of different spectrums from each other, and a light source mounting substrate  52  on which the light sources  51  are mounted on one surface thereof. The light sources  51  are arranged in a longitudinal direction on the both end sides of the liquid crystal display apparatus  100  in the lateral direction thereof, and include a plurality of LEDs. The light sources  51  are attached to the strip-shaped light source mounting substrates  52  and  52 . The light source mounting substrates  52  and  52  are disposed to face each other on the both end sides of the liquid crystal display apparatus  100  in the lateral direction thereof, respectively. 
         [0039]    That is, the light source mounting substrates  52  and  52  are disposed so that a thickness direction thereof runs along in the lateral direction, a long-side direction thereof runs along the longitudinal direction, and a short-side direction runs along a thickness direction of the liquid crystal display apparatus  100  (hereinafter, a front-back direction). The plurality of light sources  51 ,  51 , . . . and  51  are linearly disposed in the long-side direction of the light source mounting substrate  52 . The light source mounting substrate  52  is made of, for example, a metallic material such as aluminum, which has high thermal conductivity and heat dissipation, so as to efficiently transmit heat generated in the plurality of light sources  51 ,  51 , . . . and  51  and radiate it to an outside. 
         [0040]    In addition, the liquid crystal display apparatus  100  includes a pair of heat spreaders  60  and  60 , which are respectively disposed in the vicinity of the light source units  50  and  50 . The heat generated in the plurality of light sources  51 ,  51 , . . . and  51  passes through the light source mounting substrate  52 , and is diffused by the heat spreaders  60  and  60 . The heat spreader  60  has a rectangular plate-shaped plate part  61  disposed along a surface orthogonal to the front-back direction, and a rectangular plate-shaped rising part  62  (support plate) which extends from an outer end portion of the plate part  61  in the front-back direction. The heat spreader  60  has an L shape as viewed in a lateral cross-section, as illustrated in  FIG. 2 . The plate part  61  is a rectangular shape with the longitudinal direction as a long-side direction, and the lateral direction as a short-side direction. 
         [0041]    In more detail, the rising part  62  of the heat spreader  60  is disposed at the outside from the light source mounting substrate  52  in the lateral direction of the liquid crystal display apparatus  100 . The inside of the rising part  62  contacts the other surface of the light source mounting substrate  52  through the surface. A heat transfer sheet may be disposed between the light source mounting substrate  52  and the rising part  62  for improving contact properties to reduce thermal resistance. In addition, the plate part  61  is configured so as to contact with a bottom surface  71  (one surface) of the rear housing body  70  through the surface. That is, the heat spreader  60  has a function as a heat transfer member, which contacts the rear housing body  70  to transfer the heat generated in the light source unit  50  to the rear housing body  70 . 
         [0042]    The plate part  61  has a plurality of long holes  63 ,  63 , . . . and  63  formed therein by penetrating the plate part  61  in the thickness direction. As illustrated in  FIG. 1 , the long holes  63 ,  63 , . . . and  63  are formed so that a major axis direction thereof extends in the lateral direction of the liquid crystal display apparatus  100 . In other words, the major axis direction of the long holes  63 ,  63 , . . . and  63  coincides with an expansion and contraction direction of the light guide plate  40 , as described below. The long holes  63 ,  63 , . . . and  63  are juxtaposed at an inner end portion of the plate part  61  in the long-side direction of the plate part  61 . 
         [0043]    The plate part  61  has engaging protrusions  90  (engaging parts) which protrude toward the light guide plate  40  side on one surface and at both end portions thereof in the long-side direction, so as to be engaged with notches  43  of the light guide plate  40  to be described below. The engaging protrusion  90  is formed in a column shape, and is inserted into the notch  43  of the light guide plate  40 , such that the plate part  61  is engaged with the light guide plate  40 . In addition, a diameter of the engaging protrusion  90  is the same as a dimension between the opposite inner surfaces of the notch  43 . Thereby, the plate part  61  (heat spreader  60 ) may slide according to an expansion and contraction of the light guide plate  40  in the lateral direction of the liquid crystal display apparatus  100 , while sliding of the plate part  61  is restricted by the light guide plate  40 . Without limitation thereto, the diameter of the engaging protrusion  90  may be slightly smaller than the dimension between the opposite inner surfaces of the notch  43 . 
         [0044]    Meanwhile, the heat spreader  60  is made of, for example, a metal material such as aluminum, which has thermal conductivity equal to or higher than the light source mounting substrate  52 . 
         [0045]    The liquid crystal display apparatus  100  includes one rectangular plate-shaped light guide plate  40 , which is provided with the long-side direction thereof as a lateral direction. The light guide plate  40  is made of a translucent material, and is made of, for example, a transparent resin material such as acryl. The light emitted from the LEDs of the light source  51  is made incident on side surfaces  41  and  42  at both end sides of the light guide plate  40 . The side surfaces  41  and  42  of the light guide plate  40  play a role of a light incident surface which allows the light emitted from the plurality of light sources  51 ,  51 , . . . and  51  to be made incident into the light guide plate  40 , and the light made incident thereon is emitted from one surface of the light guide plate  40 . 
         [0046]    The notches  43  and  43  are formed at respective long-side edge portions of the light guide plate  40 . The notches  43  and  43  are formed in a U shape, and as described above, the engaging protrusions  90  of the heat spreader  60  are inserted into the notches  43  and  43  to engage the heat spreader  60  and the light guide plate  40  with each other. That is, the notch  43  is an engaged part to be engaged with an engaging pin  63 . 
         [0047]    The light guide plate  40  has fine convexes and concaves (not illustrated) formed on the other surface  44  thereof. The light generated from the light source  51  is irregularly reflected by these fine convexes and concaves during propagating into the light guide plate  40 . Thereby, the light made incident on the light guide plate  40  from the light source  51  is diffused, and the light is emitted from the whole of the one surface of the light guide plate  40 . The one surface of the light guide plate  40  plays a role of a light emitting surface which emits the light from the light guide plate  40  to the outside. That is, the light guide plate  40  reflects the incident light which is made incident thereon from the side surfaces  41  and  42  to emit the light from the whole of the one surface. In other words, the light guide plate  40  plays a role of an optical element for converting the light emitted from the light source  51  in which the LEDs of a dot light source are linearly arranged into a planar light source. 
         [0048]    The light guide plate  40  has a reflection plate (not illustrated) disposed on the other surface  44  side thereof. The reflection plate is disposed so as to face the other surface  44  of the light guide plate  40 , and reflects a component proceeding to the other surface  44  of the scattering light propagating inside of the light guide plate  40  to lead it to one surface side of the light guide plate  40 . 
         [0049]    Meanwhile, the optical sheet  30  is disposed on the one surface side of the light guide plate  40 . Specifically, the optical sheet  30  includes a diffusion sheet  31 , a lens sheet  32 , and a polarizing sheet  33 . Optical properties of each of these sheets are optimally adjusted for the respective functions thereof. 
         [0050]    The liquid crystal display panel  10  is disposed on a front side of the optical sheet  30 . The liquid crystal display panel  10  is a rectangular plate shape, and disposed so as to cover the polarizing sheet of the optical sheet  30 . A rear surface of the liquid crystal display panel  10  is irradiated with the light from the light guide plate  40  through the optical sheet  30 , such that an image is displayed in a display region provided on a front surface of the front side. Therefore, a user may view this image through an opening part  21  of the front housing body  20  to be described below. 
         [0051]    The front housing body  20  is disposed on the front surface side of the liquid crystal display panel  10 . The front housing body  20  has a hollow rectangular front surface part  22  in which the opening part  21  is formed at a central portion thereof, and side surface parts  23  which extend from four side edge portions of the front surface part  22  in the front-back direction. The front surface part  22  of the front housing body  20  covers a peripheral region of the liquid crystal display panel  10 , and the side surface parts  23  forms the side surfaces of the liquid crystal display apparatus  100  in the lateral direction. 
         [0052]    The rear housing body  70  is a cylindrical shape having a bottom, and has the rectangular plate-shaped bottom surface  71 , and side surface parts  76  which extend from peripheries of the bottom surface  71  in the front-back direction. Outer peripheral surfaces of the side surface parts  76  of the rear housing body  70  contact the inner peripheral surface of the side surface parts  23  of the front housing body  20  through the surface to be fixed to each other in this state. Thereby, the front housing body  20  and the rear housing body  70  form the housing of the liquid crystal display apparatus  100 . 
         [0053]    The light guide plate  40  has engaging parts (not illustrated) at side surfaces of the central portion in the long-side direction to be engaged with the side surface parts  76  (places illustrated by arrows in  FIG. 1 ) of the rear housing body  70 , and is positioned in the rear housing body  70  by appropriately engaging with the side surface parts  76 . 
         [0054]    The heat spreaders  60  and  60  are slidably held on the bottom surface  71  of the rear housing body  70 .  FIG. 3  is an explanatory view describing holding of the heat spreader  60  in the liquid crystal display apparatus  100  according to Embodiment 1 of the present invention, and  FIG. 4  is a partial cross-sectional view illustrating a cross-section taken on line A-A of  FIG. 3 . 
         [0055]    As illustrated in  FIG. 3 , the heat spreader  60  is provided so that the long-side direction of the plate part  61  is the longitudinal direction, and the one surface of the plate part  61  is provided so as to contact with the other surface  44  of the light guide plate  40  through the surface at an end portion of the light guide plate  40  in the long-side direction thereof. That is, the plate part  61  is interposed between the light guide plate  40  and the rear housing body  70  (bottom surface  71 ). Further, surface-contacting of the one surface of the plate part  61  with the other surface  44  of the light guide plate  40  at the end portion of the light guide plate  40  in the long-side direction thereof is not essential, and it may be provided to have a prescribed interval therebetween. 
         [0056]    The heat spreader  60  (plate part  61 ) is slidably held on the bottom surface  71  by the engaging pin  91 . The engaging pin  91  has a circular column-shaped body part  912  which penetrates each long hole  63  of the plate part  61 , wherein one end of the body part  912  is fixed to the bottom surface  71  of the rear housing body  70 , and the other end of the body part  912  is provided with a head portion  911  having a larger diameter than a minor axis of the long hole  63 . Thereby, it is possible to prevent the plate part  61  (heat spreader  60 ) from being separated from the bottom surface  71 , and allow the plate part  61  to slide in the major axis direction for only a distance of the major axis of the long hole  63 . 
         [0057]    In addition, the body part  912  of the engaging pin  91  is provided with a step portion  913 , and a dimension W 1  from the step portion  913  to the head portion  911  is equal to or slightly larger than a thickness of the plate part  61 . Thereby, it is possible to restrict the body part  912  of the engaging pin  91  from being inserted into the bottom surface  71  deeper than the step portion  913 , and prevent a pressing force more than necessary from being applied to the plate part  61 , such that sliding of the plate portion  61  in the major axis direction of the plate part  61  may be ensured. 
         [0058]    Further, as described above, the engaging protrusion  90  (engaging part) provided in the plate part  61  is inserted into the notch  43  (engaged part) of the light guide plate  40 , and the plate part  61  is engaged with the light guide plate  40 , such that sliding of the plate part  61  (heat spreader  60 ) in the lateral direction is restrained by the light guide plate  40 . 
         [0059]    Since the liquid crystal display apparatus  100  according to Embodiment 1 of the present invention has the above-described configuration, it is possible to solve the problems caused by varying an interval between the light source  51  and the incident surface (side surfaces  41  and  42 ) of the light guide plate  40  due to the thermal expansion of the light guide plate  40 . Hereinafter, this will be described in detail using  FIG. 3 . 
         [0060]    That is, in the liquid crystal display apparatus  100  according to Embodiment 1 of the present invention, as described above, since the central portion of the light guide plate  40  in the long-side direction thereof is engaged with the side surface parts  76  of the rear housing body  70 , the light guide plate  40  may be extended or contracted from the central portion to the both end sides (a direction illustrated by an arrow in  FIG. 3 ) in the long-side direction, or toward the central portion in the long-side direction. 
         [0061]    For example, when the light guide plate  40  is thermally expanded, the light guide plate  40  may be extended in a direction in which the side surface  41  is approach the light source  51  (hereinafter, referred to as an extension direction). Meanwhile, the plate part  61  is engaged with the light guide plate  40  by the engaging protrusion  90  provided in the plate part  61  and the notch  43  of the light guide plate  40 , such that, at this time, a force is applied to the heat spreader  60  in the extension direction. Further, the plate part  61  (heat spreader  60 ) is configured so as to slide in the major axis direction of the long hole  63 , that is, in the extension direction, while separating from the bottom surface  71  is prevented by the engaging pin  91 , such that the heat spreader  60  slides on the bottom surface  71  by the force applied thereto in the extension direction. Accordingly, when the light guide plate  40  is expanded due to heat, it is possible to maintain the interval between the light source  51  and the side surface  41  of the light guide plate  40 , thus to solve the problems caused by varying the interval. 
         [0062]    In addition, when the light guide plate  40  is contracted, similarly, the plate part  61  is engaged with the light guide plate  40 , such that the heat spreader  60  may slide on the bottom surface  71  in the contraction direction according to the contraction of the light guide plate  40 . Also in this case, it is possible to maintain the interval between the light source  51  and the side surface  41  of the light guide plate  40 , thus to solve the problems caused by varying the interval. 
         [0063]    Further, in the liquid crystal display apparatus  100  according to Embodiment 1 of the present invention, the notches  43  and  43  are provided in the vicinity of the side surfaces  41  and  42  of the light guide plate  40 . A dimension W 2  from the side surfaces  41  and  42  to the notches  43  of the light guide plate  40  is 20 mm, for example. In this way, the notches  43  and  43  are disposed on the side surfaces  41  and  42  side of the light guide plate  40  as much as possible, thereby it is possible to minimize a variation in the interval between the side surface  41  of the light guide plate  40  and the light source  51  due to the end portion relating to the dimension W 2  in the light guide plate  40  being thermally expanded. 
       Embodiment 2 
       [0064]    In the liquid crystal display apparatus  100  (light source device  1 ) according to Embodiment 1 of the present invention, the case in which the engaging protrusion  90  of the heat spreader  60  is inserted into the notches  43  and  43 , and the heat spreader  60  and the light guide plate  40  are engaged with each other has been described, by way of example, but the present invention is not limited thereto. 
         [0065]      FIG. 5  is a partial cross-sectional view describing a relation between the heat spreader  60  and the light guide plate  40  in a liquid crystal display apparatus  100  according to Embodiment 2 of the present invention. 
         [0066]    In the liquid crystal display apparatus  100  according to Embodiment 2 of the present invention, a double-sided tape  80  is interposed between the light guide plate  40  and the plate part  61  of the heat spreader  60 , and the plate part  61  is adhered to the light guide plate  40 . That is, in Embodiment 2 of the present invention, the heat spreader  60  (plate part  61 ) is slidably held on the bottom surface  71  by the double-sided tape  80 , and thereby, the plate part  61  (heat spreader  60 ) slides on the bottom surface  71  according to the expansion and contraction of the light guide plate  40 . 
         [0067]    In the liquid crystal display apparatus  100  according to Embodiment 2 of the present invention, the other configuration is the same as that of Embodiment 1, and therefore will not be described in detail. 
         [0068]    Since the liquid crystal display apparatus  100  according to Embodiment 2 of the present invention has the configuration as described above, it is possible to solve the problems caused by varying the interval between the light source  51  and the incident surface (side surfaces  41  and  42 ) of the light guide plate  40 , due to being thermally expanded the light guide plate  40  caused by heat generated during operating. 
         [0069]    For example, when the light guide plate  40  is thermally expanded, the light guide plate  40  may be extended in a direction in which the side surface  42  approaches the light source  51  (hereinafter, referred to as an extension direction) (see  FIG. 5 ). Meanwhile, the plate part  61  is adhered to the light guide plate  40  by the double-sided tape  80 , such that, at this time, a force is applied to the heat spreader  60  in the extension direction. In addition, the plate part  61  (heat spreader  60 ) is configured so as to slide in the major axis direction of the long hole  63 , that is, in the extension direction, while separating from the bottom surface  71  is prevented by the engaging pin  91 , such that the heat spreader  60  slides on the bottom surface  71  by the force applied thereto in the extension direction. Accordingly, when the light guide plate  40  is expanded due to heat, it is possible to maintain the interval between the light source  51  and the side surfaces  41  and  42  of the light guide plate  40 , thus to solve the problems caused by varying the interval. Further, these operation and effect are the same as the case of contracting the light guide plate  40 , and therefore will not be described in detail. 
         [0070]    The same parts as those in Embodiment 1 will be denoted by the same reference numerals, and will not be described. 
       Embodiment 3 
       [0071]    A liquid crystal display apparatus  100  (light source device  1 ) according to Embodiment 3 has substantially the same configuration as Embodiments 1 and 2, and similar to Embodiments 1 and 2, is configured so that the heat spreader  60  slides according to the expansion and contraction of the light guide plate  40 . 
         [0072]    However, the liquid crystal display apparatus  100  according to Embodiment 3 is configured so that sliding of the heat spreader  60  according to the expansion and contraction of the light guide plate  40  is performed by a mechanism different from Embodiments 1 and 2, which will be described in detail below. 
         [0073]      FIG. 6  is a partial cross-sectional view describing a relation between the heat spreader  60  and the light guide plate  40  in a liquid crystal display apparatus  100  according to Embodiment 3 of the present invention, and  FIG. 7  is a partial cross-sectional view illustrating a cross-section taken on line B-B of  FIG. 6 . 
         [0074]    The liquid crystal display apparatus  100  according to Embodiment 3 of the present invention includes an abutting part  53  which is provided in the light source mounting substrate  52  to abut the light guide plate  40 , and a pulling spring  75  for pulling the heat spreader  60  toward the center side of the light guide plate  40  in the long-side direction thereof. 
         [0075]    The abutting part  53  is provided on at least one end portion of the light source mounting substrate  52  in the long-side direction thereof. In more detail, the abutting part  53  is provided at one end portion of the light source mounting substrate  52 , and in the vicinity of the end portions of the side surfaces  41  and  42  of the light guide plate  40  in the long-side direction thereof. The abutting part  53  protrudes in a direction perpendicular to the surface of the light source mounting substrate  52 , and has a larger dimension in this direction than the LED of the light source  51 . Accordingly, when the light guide plate  40  is thermally expanded in the light source  51  side, the abutting part  53  abuts the side surfaces  41  and  42  of the light guide plate  40  abut in advance of the light source  51 , such that further narrowing the interval between the side surfaces  41  and  42  and the light source  51  may be prevented, while the interval is maintained. 
         [0076]    The spring  75  is a so-called coil spring, and includes hooks at both ends of a coil part, respectively. A rectangular cut-away part  72  in which the spring  75  is located is formed in the bottom surface  71  of the rear housing body  70  on the side surface part  76  side in the vicinity of the plate part  61 . The cut-away part  72  is formed to a portion facing the inner end portion of the plate part  61  in the bottom surface  71 , and a portion of the plate part  61  may be viewed through the cut-away part  72  of the bottom surface  71 . 
         [0077]    In this way, a surface (hereinafter, the other surface) of the plate part  61  viewed through the cut-away part  72  is provided with a locked protrusion  73  which protrudes toward the bottom surface  71  in the vicinity of the one short side of the cut-away part  72 . In addition, the bottom surface  71  in the vicinity of the other short side of the cut-away part  72  is provided with a locked protrusion  74  which protrudes outward in the direction perpendicular to the bottom surface  71 . 
         [0078]    The spring  75  is placed within the cut-away part  72 , and one hook thereof is hooked to the locked protrusion  73 , and the other hook thereof is hooked to the locked protrusion  74 . Accordingly, a tensile force of a prescribed magnitude is always applied to the plate part  61  by the spring  75  from the locked protrusion  73  to the locked protrusion  74  direction. In addition, such a mechanism including the spring  75  is provided at four corners of the rear housing body  70 . Further, the present invention is not limited thereto. The mechanism including the spring  75  may be configured in such a manner that they are provided at a total of two places one by one at the center sides of the respective heat spreaders  60  (plate parts  61 ), and they are provided at a total of six places at the four corners of the rear housing body  70  and the center sides of the respective heat spreaders  60  (plate parts  61 ), without limitation in the place and the number thereof. 
         [0079]    The liquid crystal display apparatus  100  according to Embodiment 3 of the present invention is not limited to the above-described configuration, and may be configured so as to use a leaf spring instead of the coil spring. 
         [0080]    Since the liquid crystal display apparatus  100  according to Embodiment 3 of the present invention has the configuration as described above, it is possible to solve the problems caused by varying the interval between the light source  51  and the incident surface (side surfaces  41  and  42 ) of the light guide plate  40 , due to being thermally expanded the light guide plate  40  caused by heat generated during operating. 
         [0081]    In the liquid crystal display apparatus  100  according to Embodiment 3 of the present invention, as described above, the light guide plate  40  may be extended from the central portion to the both end sides in the long-side direction, and contracted toward the central portion. 
         [0082]    For example, when the light guide plate  40  is thermally expanded, the light guide plate  40  may be extended in a direction in which the side surfaces  41  and  42  approach the light source  51  (hereinafter, referred to as an extension direction) (see  FIG. 5 ). When the light guide plate  40  is extended at a prescribed distance, the side surfaces  41  and  42  of the light guide plate  40  abut the abutting part  53 . Meanwhile, as described above, the tensile force is applied to the plate part  61  by the spring  75  in a direction opposite to the extension direction, but this tensile force is smaller than a force due to the extension of the light guide plate  40 . Accordingly, the light guide plate  40  is continuously extended in the extension direction, with the side surfaces  41  and  42  abutting the abutting part  53 , that is, while pressing the abutting part  53 . 
         [0083]    In addition, the plate part  61  (heat spreader  60 ) is configured so as to slide in the major axis direction of the long hole  63 , while separating from the bottom surface  71  is prevented by the engaging pin  91 , such that the heat spreader  60  slides on the bottom surface  71  by the force applied thereto in the extension direction, but also in this case, the interval between the side surfaces  41  and  42  of the light guide plate  40  and the light source  51  may be maintained by the abutting part  53 . 
         [0084]    On the other hand, when the operation of the liquid crystal display apparatus  100  is ended, and the light guide plate  40  is contracted, the force relating to the extension of the light guide plate  40  does not reach the heat spreader  60  (abutting part  53 ), and only the tensile force in the direction opposite to the extension direction is exclusively applied thereto by the spring  75 . 
         [0085]    Accordingly, when the light guide plate  40  is contracted, the heat spreader  60  (plate part  61 ) is pulled in the direction opposite to the extension direction by the spring  75 . In this case, the light guide plate  40  is contracted in the direction opposite to the extension direction, with abutting the abutting part  53 , such that the interval between the side surfaces  41  and  42  of the light guide plate  40  and the light source  51  is maintained by the abutting part  53 . 
         [0086]    From the above description, when the light guide plate  40  is extended or contracted, the interval between the light source  51  and the side surfaces  41  and  42  of the light guide plate  40  is maintained, thus solving the problems caused by varying the interval. 
         [0087]    The same parts as those in Embodiment 1 will be denoted by the same reference numerals, and will not be described. 
       Embodiment 4 
       [0088]    A liquid crystal display apparatus  100  (light source device  1 ) according to Embodiment 4 has substantially the same configuration as Embodiments 1 and 2, and similar to Embodiments 1 and 2, is configured so that the heat spreader  60  slides according to the expansion and contraction of the light guide plate  40 . 
         [0089]    However, the liquid crystal display apparatus  100  according to Embodiment 4 is configured so that sliding of the heat spreader  60  according to the expansion and contraction of the light guide plate  40  is performed by a mechanism different from Embodiments 1 and 2, which will be described in detail below. 
         [0090]      FIG. 8  is a partial cross-sectional view describing a relation between the heat spreader  60  and the light guide plate  40  in a liquid crystal display apparatus  100  according to Embodiment 4 of the present invention. 
         [0091]    The liquid crystal display apparatus  100  according to Embodiment 4 of the present invention includes an abutting part  54  which is provided in the light source mounting substrate  52  to abut the light guide plate  40 , and a spring  77  for pressing the heat spreader  60  toward the center of the light guide plate  40  in the long-side direction thereof. 
         [0092]    The abutting part  54  has, for example, a circular column-shape, and is provided at least one end portion of the light source mounting substrate  52  in the long-side direction thereof. In more detail, the abutting part  54  is provided at one end portion of the light source mounting substrate  52  and in the vicinity of the end portions of the side surfaces  41  and  42  of the light guide plate  40  in the long-side direction thereof. The abutting part  54  protrudes in a direction perpendicular to the surface of the light source mounting substrate  52 , and has a larger dimension in this direction than the LED of the light source  51 . 
         [0093]    The spring  77  is provided at the outside of the rising part  62  of the heat spreader  60 . In more detail, the spring  77  is interposed on the bottom surface  71  of the rear housing body  70  between the rising part  62  and the side surface part  76  of the rear housing body  70 . In addition, the spring  77  is a so-called coil spring, and is disposed so that the expansion and contraction direction thereof is the same direction as the expansion and contraction direction of the light guide plate  40 . 
         [0094]    In addition, a pressing force of a prescribed magnitude is always applied to the plate part  61  by the spring  77  toward the center of the light guide plate  40  in the long-side direction thereof. Accordingly, the abutting part  54  always abuts the side surfaces  41  and  42  of the light guide plate  40 . That is, when the light guide plate  40  is either thermally expanded in the light source  51  side, or contracted toward the center in the long-side direction thereof, the abutting part  54  abuts the side surfaces  41  and  42  of the light guide plate  40 , such that further narrowing the interval between the side surfaces  41  and  42  and the light source  51  may be prevented, while the interval is maintained. 
         [0095]    The spring  77  is provided at the outside of the rising part  62  of the respective heat spreader  60  on at least one place, but it is not limited thereto, and the spring  77  may be provided at two places or more. Further, the spring  77  is not limited to the coil spring, and may be configured so as to use a leaf spring instead of the coil spring. 
         [0096]    Since the liquid crystal display apparatus  100  according to Embodiment 4 of the present invention has the configuration as described above, it is possible to solve the problems caused by varying the interval between the light source  51  and the incident surface (side surfaces  41  and  42 ) of the light guide plate  40 , due to the thermal expansion of the light guide plate  40  caused by heat generated during operating. 
         [0097]    In the liquid crystal display apparatus  100  according to Embodiment 4 of the present invention, as described above, the light guide plate  40  may be extended from the central portion to the both end sides in the long-side direction, and contracted toward the central portion. 
         [0098]    For example, when the light guide plate  40  is thermally expanded, the light guide plate  40  may be extended in a direction in which the side surface  41  and  42  of the light guide plate  40  approach the light source  51  (hereinafter, referred to as an extension direction) (see  FIG. 5 ). Meanwhile, as described above, the pressing force is applied to the plate part  61  by the spring  77  to a side opposite to the extension direction of the light guide plate  40 , and the abutting part  54  always abuts the side surfaces  41  and  42  of the light guide plate  40 , but this pressing force is smaller than the force due to the extension of the light guide plate  40 . Accordingly, the light guide plate  40  is continuously extended in the extension direction, with the side surfaces  41  and  42  abutting the abutting part  54 . 
         [0099]    In addition, the plate part  61  (heat spreader  60 ) is configured so as to slide in the major axis direction of the long hole  63 , while separating from the bottom surface  71  is prevented by the engaging pin  91 , such that the heat spreader  60  slides on the bottom surface  71  by the force applied thereto in the extension direction, but also in this case, the interval between the side surfaces  41  and  42  of the light guide plate  40  and the light source  51  may be maintained by the abutting part  54 . 
         [0100]    On the other hand, when the light guide plate  40  is contracted, the force due to the extension of the light guide plate  40  is not applied to the heat spreader  60 , and only the pressing force in the direction opposite to the extension direction is exclusively applied to the heat spreader  60  by the spring  77 . Accordingly, when the light guide plate  40  is contracted, the heat spreader  60  (plate part  61 ) is pressed in the direction opposite to the extension direction by the spring  77 . 
         [0101]    Thereby, the light guide plate  40  is contracted in the direction opposite to the extension direction, with abutting the abutting part  54 , and the heat spreader  60  (plate part  61 ) also moves in this direction, such that the interval between the side surfaces  41  and  42  of the light guide plate  40  and the light source  51  is be maintained. 
         [0102]    In the above description, the case in which the light source  51  is disposed on the both end sides of the liquid crystal display apparatus  100  in the lateral direction thereof has been described, by way of an example, but the present invention is not limited thereto. For example, the light source  51  may be configured to be disposed on the both end sides of the liquid crystal display apparatus  100  in the longitudinal direction thereof, and may be configured to be disposed at the respective both end sides of the liquid crystal display apparatus  100  in the longitudinal and lateral directions thereof. 
         [0103]    The same parts as those in Embodiment 1 will be denoted by the same reference numerals, and will not be described. 
         [0104]    As this invention may be embodied in several forms without departing from the spirit of essential characteristics thereof, the present embodiments are therefore illustrative and not restrictive, since the scope of the invention is defined by the appended claims rather than by the description preceding them, and all changes that fall within metes and bounds of the claims, or equivalence of such metes and bounds thereof are therefore intended to be embraced by the claims.