Patent Publication Number: US-2020278488-A1

Title: Illumination device and display device

Description:
TECHNICAL FIELD 
     The technique disclosed herein relates to an illumination device and a display device including a light guide plate provided with a cutout portion such as a hole and a recessed portion. 
     BACKGROUND ART 
     In recent years, liquid crystal display devices including liquid crystal panels have been utilized as display devices for electronic devices such as information terminals and instruments provided in vehicles such as automobiles and the like. Since the liquid crystal panel does not emit light itself, external light needs to be utilized to display an image. Thus, this type of display device includes, in addition to the liquid crystal panel, an illumination device (so-called backlight device) for supplying light to the liquid crystal panel. The backlight device is disposed on a back face side of the liquid crystal panel, and is configured to irradiate the back face of the liquid crystal panel with light spread in a planar shape. 
     As the backlight device, for example, as disclosed in PTL1, an edge light type (or side light type) is known that is provided with a light guide plate made from a transparent plate-shaped member and a light source (for example, LED) disposed to face an end face of the light guide plate. Light emitted from the light source of the backlight device is incident on the light guide plate from the end face of the light guide plate (hereinafter, referred to as a light incident surface) facing the light source. Then, the light propagates through the light guide plate, and is emitted from a front side plate surface (light exit surface) as a planar light. 
     CITATION LIST 
     Patent Literature 
     PTL1: JP 2013-149559A 
     SUMMARY OF INVENTION 
     Technical Problem 
     However, in an edge light type backlight device as disclosed in PTL1, a light guide plate configured to include, for example, a portion cut out such as a hole or a recessed portion (referred to as a cutout portion) has a problem that a light incident on the light guide plate from a light incident surface and traveling linearly toward a counter light incident surface opposite to the light incident surface is blocked on a path of light by the cutout portion, and therefore, brightness of a region on a counter light incident surface side is reduced than brightness of the cutout portion to generate a brightness unevenness. 
     In order to solve such a brightness unevenness, a configuration is conceivable in which the light source is provided also on the counter light incident surface side, but such a configuration adds complexity in configuration due to the arrangement of light source, and thus increases a size and cost of the backlight device. 
     The technique disclosed herein is achieved based on the above-described circumstances, and an object of the present invention is to provide an illumination device and a display device in which brightness unevenness is suppressed even when the light guide plate is provided with a cutout portion. 
     Solution to Problem 
     (1) An embodiment of the present invention is an illumination device including: a light source; and a light guide plate configured to guide light from the light source, wherein the light guide plate includes a light incident surface on which the light from the light source is incident, a counter light incident surface opposite to the light incident surface, a light exit surface that is one of a pair of plate surfaces and outputs the light, and a counter light exit surface opposite to the light exit surface, and is provided with a cutout portion with a portion partially cut out, at least one of the pair of plate surfaces of the light guide plate is provided with an auxiliary light guide plate, the auxiliary light guide plate being configured with a plate-shaped member extending from the light incident surface to a region between the cutout portion and the counter light incident surface, an auxiliary light guide plate-side light incident surface, among end faces of the auxiliary light guide plate, disposed on the light incident surface side is provided with an auxiliary light source, the auxiliary light source being configured to emit light toward the auxiliary light guide plate-side light incident surface, and a region, of the auxiliary light guide plate, overlapping the region of the light guide plate between the cutout portion and the counter light incident surface is a light exit section, the light exit section being configured to output light from the auxiliary light source toward the region of the light guide plate between the cutout portion and the counter light incident surface. 
     (2) An embodiment of the present invention is the illumination device according to the configuration in (1) described above, wherein the auxiliary light guide plate is disposed to overlap the counter light exit surface of the light guide plate. 
     (3) An embodiment of the present invention is the illumination device according to the configuration in (1) or (2) described above, wherein the light incident surface of the light guide plate and the auxiliary light guide plate-side light incident surface of the auxiliary light guide plate are disposed to be overlapped with each other. 
     (4) An embodiment of the present invention is the illumination device according to the configuration in any one of (1) to (3) described above, wherein the auxiliary light guide plate is disposed to entirely overlap the light guide plate. 
     (5) An embodiment of the present invention is the illumination device according to the configuration in any one of (1) to (4) described above, wherein the cutout portion is a through-hole penetrating the light guide plate. 
     (6) An embodiment of the present invention is the illumination device according to the configuration in (5) described above, wherein the auxiliary light guide plate is formed into a U-shape including a pair of linear portions and a bent portion, the pair of linear portions extending from the light incident surface to a lateral side portions of the through-hole, and the bent portion being curved or bent to wrap around inward the through-hole continuously from the linear portions. 
     (7) An embodiment of the present invention is the illumination device according to the configuration in (6) described above, wherein a reflection sheet that reflects light is provided on an end face on an outer peripheral side of the bent portion. 
     (8) An embodiment of the present invention is the illumination device according to the configuration in any one of (1) to (4) described above, wherein the cutout portion is a recessed portion recessed concavely from a side edge of the light guide plate. 
     (9) An embodiment of the present invention is a display device including the illumination device according to any one of (1) to (8) described above, and a display panel configured to perform display by using light from the illumination device. 
     (10) An embodiment of the present invention is the display device according to the configuration in (9) described above, wherein the display panel includes a panel cutout portion cut out along the cutout portion at a position corresponding to the cutout portion. 
     Advantageous Effects of Invention 
     According to the technique disclosed herein, the illumination device and the display device can be achieved in which brightness unevenness is suppressed even in a case that the light guide plate is provided with a cutout portion such as a hole and a recessed portion. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is an exploded perspective view illustrating a liquid crystal display device according to a first embodiment. 
         FIG. 2  is a back view of a light guide plate and an LED. 
         FIG. 3  is a perspective view of a main portion of a back face side of a backlight device. 
         FIG. 4  is a back view of the main portion of the backlight device. 
         FIG. 5  is a back view of an auxiliary light guide plate and an auxiliary LED. 
         FIG. 6  is a cross-sectional view taken along a line A-A of  FIG. 4 . 
         FIG. 7  is a perspective view of a main portion of a back face side of a backlight device with a reflection sheet being omitted according to a second embodiment. 
         FIG. 8  is a back view of the main portion of the backlight device with the reflection sheet being omitted. 
         FIG. 9  is a cross-sectional view of a light guide plate, an auxiliary light guide plate, and a reflection sheet according to another embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     First Embodiment 
     The first embodiment will be described with reference to  FIGS. 1 to 6 . In the present embodiment, a liquid crystal display device  10  (one example of a display device) including a liquid crystal panel  11  (one example of a display panel) capable of displaying an image and a backlight device  20  (one example of an illumination device) supplying light for display to the liquid crystal panel  11  is illustrated. Note that an X-axis, a Y-axis, and a Z-axis are illustrated in a part of each drawing, and illustration is made so that the respective directions correspond to directions illustrated in each drawing. A vertical direction is based on a vertical direction in  FIG. 1 , an upper side in  FIG. 1  is referred to as a front side, and a lower side of  FIG. 1  is referred to as a rear side. An X-axis direction is a width direction or a lateral direction, a Y-axis direction is a length direction, and a Z-axis direction is a thickness direction. 
     The liquid crystal display device  10  according to the present embodiment is generally rectangular in a planar view and formed into substantially a block shape, in which the liquid crystal panel  11  and the backlight device  20  disposed on the rear side of the liquid crystal panel  11  are integrally formed with each other via a double-sided tape or the like. The liquid crystal display device  10  according to the present embodiment is, for example, mounted on a dashboard of an automobile for use, configures a part of an instrument panel, and can display a part of an instrument of an instrument panel, various warning images, a map image of a car navigation system, an image captured by an onboard camera, and the like. 
     The liquid crystal panel  11  has a rectangular plate shape, and although a detailed illustration thereof is omitted, the liquid crystal panel  11  has a well-known configuration in which a pair of transparent glass substrates (having high translucency) are adhered to each other with a predetermined gap interposed therebetween, and a liquid crystal layer is disposed between both glass substrates. One glass substrate is provided with a switching element (for example, TFT) connected to a source wiring line and a gate wiring line that are orthogonal to each other, a pixel electrode connected to the switching element, and further, an alignment film or the like, and the other glass substrate is provided with a color filter in which colored parts of R (red), G (green), and B (blue) are arranged in a predetermined arrangement, a counter electrode, an alignment film, or the like. Among these, image data and various control signals necessary to display images from a drive circuit substrate are supplied to the source wiring line, the gate wiring line, the counter electrode, and the like. A polarizer is disposed on an outer side of both glass substrates. 
     The liquid crystal panel  11  can display an image by using light supplied from the backlight device  20 , and a front side thereof is a light exit side. Note that a short side direction of the liquid crystal panel  11  coincides with the X-axis direction, a long side direction coincides with the Y-axis direction, and the thickness direction coincides with the Z-axis direction. 
     A panel through-hole  12  (one example of a panel cutout portion) passes through the liquid crystal panel  11  according to the present embodiment. The panel through-hole  12  is in mutual communication with a device through-hole  32  of the backlight device  20  described below, and is for passing an object such as a needle of a mechanical instrument provided in the instrument panel disposed on the rear side of the liquid crystal display device  10 . A hole edge portion of the panel through-hole  12  is sealed by a sealing member so that liquid crystals do not leak out. 
     The backlight device  20 , like the liquid crystal panel  11 , is generally rectangular in a planar view and formed into substantially a block shape. The backlight device  20  includes at least a plurality of LEDs  21  (Light Emitting Diode) as light sources and a LED substrate having the LEDs  21  provided thereon, a light guide plate  25  that guides light emitted from the LED  21 , a plurality of optical sheets  30  layered on a front side of the light guide plate  25 , and a reflection sheet  35  disposed on a rear side of the light guide plate  25 . 
     The backlight device  20  is a one-side light incident edge light type (side light type) in which the LEDs  21  are disposed on the end face of one short side of the light guide plate  25  such that the light is incident on the light guide plate  25  from only one side. The backlight device  20  is configured to convert lights from the LEDs  21  into planar lights to emit toward the liquid crystal panel  11  on the front side. In other words, the backlight device  20  has a front side as a light exit side. Components of the backlight device  20  will be described below. 
     The LED  21  has a configuration in which a LED chip (LED element) that is a semiconductor light emitting element is sealed, with a resin material, on a substrate portion fixed to a plate surface of the LED substrate, which will be described later. The LED chip mounted on the substrate portion used here has one kind of main light emission wavelength, and specifically, emits one color light of blue light. On the other hand, the resin material sealing the LED chip contains a phosphor dispersed therein that is excited by the blue light emitted from the LED chip to emit the light of a predetermined color, and generally emits white light. This LED  21  is a so-called side light emitting type in which a side surface thereof adjacent to the mounting surface of the LED substrate is a light-emitting face. 
     The LED  21  emits light having a predetermined spread (directionality) centered on an optical axis L from the light-emitting face. In the case of the present embodiment, the light axis L of the emitted light is substantially perpendicular to the central portion of the light-emitting face and coincides with the Y-axis direction. Therefore, among the lights from LED  21 , light traveling toward the end face (counter light incident surface  25 B and a pair of side surfaces  25 E) other than the light incident surface  25 A of the light guide plate  25  described below is larger in amount on the counter light incident surface  25 B than the pair of side surfaces  25 E. 
     The LED substrate has a configuration in which a plurality of LEDs  21  are mounted and arranged at intervals on surface of a film-like (sheet-like) base material that is made of an insulating material and has flexibility, and a wiring pattern for supplying power to the LEDs  21  is patterned. The LED substrate is disposed such that the light-emitting faces of the mounted LEDs  21  face the light incident surface  25 A of the light guide plate  25  in parallel. 
     Next, the light guide plate  25  will be described. The light guide plate  25  may be formed from a material having a sufficiently higher refractive index than air and excellent translucency, for example, a resin such as transparent acrylic or polycarbonate, or a variety of glass. The light guide plate  25  according to the present embodiment is formed from an acrylic resin and, as illustrated in  FIG. 1 , has a rectangular plate shape. The light guide plate  25  has a short side direction, a long side direction, and a thickness direction corresponding to the X-axis direction, the Y-axis direction, and the Z-axis direction, respectively. 
     An end face of outer peripheral end faces of the light guide plate  25  on the short side on the right back side thereof illustrated in  FIG. 1  is a light incident surface  25 A that faces the light-emitting face of LED  21  in parallel and on which light from LED  21  is incident. In the present embodiment, an end face opposite to the light incident surface  25 A (an end face on a left front side in  FIG. 1 ) is a counter light incident surface  25 B, an upper face (front surface) of the pair of plate surfaces is a light exit surface  25 C that outputs light toward the liquid crystal panel  11 , and a lower face (rear face) of the pair of plate surfaces is referred to as a counter light exit surface  25 D. Furthermore, end faces of the outer peripheral end faces of the light guide plate  25  on the long side thereof (the end faces other than the light incident surface  25 A and the counter light incident surface  25 B) are referred to as a pair of side surfaces  25 E. 
     As illustrated in  FIG. 2 , an uneven pattern having a plurality of lenticular protrusions  28  protruding toward the rear side is provided on the counter light exit surface  25 D of the light guide plate  25 . The sparser the uneven pattern is, the closer to the light incident surface  25 A side (the left side in  FIG. 2 ), and the denser gradually, the closer to the opposite side (the counter light incident surface  25 B side). According to such a configuration, each light guide plate  25  has a function of introducing light from the light incident surface  25 A and raising the light up along the Z-axis direction by the uneven pattern while propagating the light therein, and outputting the light from the light exit surface  25 C toward the front side (liquid crystal panel  11  side). 
     The light guide plate  25  is disposed right under the liquid crystal panel  11  with the optical sheet  30  interposed therebetween, and is provided with a light guide plate through-hole  26  (an example of the cutout portion) at a position corresponding to the panel through-hole  12  described above, in a state in which the liquid crystal panel  11  and the light guide plate  25  are assembled at correct positions. Specifically, as illustrated in  FIG. 2 , the light guide plate through-hole  26  is provided in the center portion in the width direction (X-axis direction) and the length direction (Y-axis direction) of the light guide plate  25 . 
     As illustrated in  FIG. 1 , three layers of the optical sheet  30  are stacked on the light exit surface  25 C of the light guide plate  25 . The optical sheet  30  has a flat rectangular sheet shape, and a short side direction and long side direction thereof coincide with the X-axis direction and the Y-axis direction, respectively. The optical sheet  30  is disposed to be interposed between the light guide plate  25  and the liquid crystal panel  11  so as to transmit the emission light from the light guide plate  25  and deliver the transmitted light to the liquid crystal panel  11  while imparting a predetermined optical effect to the transmitted light. 
     The optical sheet  30  according to the present embodiment includes a diffuser sheet  30 A, a lens sheet  30 B, and a reflective polarizing sheet  30 C which are layered in order from a lower layer side. The sheets  30 A,  30 B, and  30 C are provided with sheet through-holes  31 A,  31 B, and  31 C, respectively, at positions corresponding to the light guide plate through-hole  26 . Hereinafter, a through-hole formed by these sheet through-holes  31 A,  31 B, and  31 C, and the light guide plate through-hole  26  is referred to as a device through-hole  32 . 
     Here, in the edge light type backlight device  20 , in the configuration as described above in which the light guide plate through-hole  26  that penetrates the plate surface is provided in the light guide plate  25 , a portion of light having directionality incident on the light guide plate  25  from the light incident surface  25 A is blocked on an optical path thereof by an object not illustrated in the drawings that is inserted through the light guide plate through-hole  26  or the light guide plate through-hole  26  itself. Therefore, a region of the light guide plate  25  closer to the counter light incident surface  25 B than the light guide plate through-hole  26 , that is, a region between the light guide plate through-hole  26  and the counter light incident surface  25 B, is an obscured portion  27  which is not easily reached by light (see  FIG. 2 ). More specifically, the obscured portion  27  includes a region which is hardly reached by light that is slight adjacent to the light guide plate through-hole  26 , and a region that is slightly away from the light guide plate through-hole  26 , illuminated a little although with low brightness, which is not reached by light that travels straight along the optical axis (Y-axis), but is reached by light that travels straight in an oblique direction without along the optical axis or by a portion of light reflected by the side surface  25 E. The obscured portion  27  generates a brightness unevenness in the backlight device  20 . 
     To address such a problem, the backlight device  20  according to the present embodiment includes an auxiliary light guide plate  40  having an external shape different from the light guide plate  25 . The auxiliary light guide plate  40  is made of an acrylic resin similarly to the light guide plate  25 , and is generally formed into a U-shape, is entirely overlaid on the lower face of the light guide plate  25  (the counter light exit surface  25 D, the surface opposite to the liquid crystal panel  11 ), and is integrally formed with the light guide plate  25 , for example, by a light-transmissive adhesive or the like, as illustrated in  FIGS. 3 to 5 , for example. 
     Specifically, the auxiliary light guide plate  40  is formed into a U-shape including a pair of parallel linear portions  41  and a curved portion (one example of a bent portion)  42 , the pair of linear portions  41  being disposed to extend linearly from the light incident surface  25 A of the light guide plate  25  to the counter light incident surface  25 B side when the light guide plate  25  is seen in a plan view to sandwich the light guide plate through-hole  26  from the lateral sides (in the width direction), the curved portion  42  being curved in a semi-circular shape to wrap around the light guide plate through-hole  26  from the lateral sides of the light guide plate through-hole  26  from the obscured portion  27  side to connect the pair of linear portions  41 . An inner peripheral edge of the curved portion  42  is configured to coincide with a hole edge portion of the light guide plate through-hole  26 . With such a configuration, a portion of the curved portion  42  of the auxiliary light guide plate  40  (a center portion) is in a state of being overlaid on a region of the obscured portion  27  adjacent to the light guide plate through-hole  26  (see  FIG. 4 ). 
     Among outer peripheral end faces of the auxiliary light guide plate  40  formed into a U-shape, an end face being overlaid on the light incident surface  25 A of the light guide plate  25  described above is an auxiliary light guide plate-side light incident surface  40 A, and an auxiliary LED  45  that emits light toward the auxiliary light guide plate  40  is disposed to face the auxiliary light guide plate-side light incident surface  40 A. In other words, the light incident surfaces  25 A and  40 A of the light guide plate  25  and the auxiliary light guide plate  40 , respectively, are overlaid with each other to face the same direction, and the LED  21  and the auxiliary LED  45  can be collectively disposed in a state of being overlaid with each other on one side of the light guide plate  25  and the auxiliary light guide plate  40 . 
     Furthermore, a region, in a lower face of the auxiliary light guide plate  40  (referred to as an auxiliary light guide plate-side counter light exit surface  40 D) of the auxiliary light guide plate  40 , that overlaps the obscured portion  27  in a state in which the auxiliary light guide plate  40  is overlaid on the light guide plate  25  is provided with an uneven pattern having a plurality of lenticular protrusions  43  protruding toward the rear side (see  FIG. 5 ). With such a configuration, the auxiliary light guide plate  40  introduces light from the auxiliary LED  45  through the auxiliary light guide plate-side light incident surface  40 A and propagates the light therein, and thereafter, raises the light by the uneven pattern (lenticular protrusion  43 ) of the curved portion  42  up along the Z-axis direction to output the light toward the front side (the liquid crystal panel  11  side, that is, the auxiliary light guide plate-side light exit surface  40 C). Hereinafter, the region of the auxiliary light guide plate  40  where light is output by the uneven pattern is referred to as a light exit section  44 . Note that, a region of the auxiliary light guide plate  40  other than the region overlapping the obscured portion  27  is not provided with the uneven pattern. In  FIGS. 3, 4, and 6 , the uneven pattern (lenticular protrusion  43 ) is omitted. 
     The backlight device  20  according to the present embodiment includes the reflection sheet  35 . The reflection sheet  35  is disposed on the rear face of the entire light guide plate including the light guide plate  25  and the auxiliary light guide plate  40 . Specifically, the reflection sheet  35  includes, in the counter light exit surface  25 D of the light guide plate  25 , at least a first reflecting portion  35 A layered on a region other than a region overlaid by the auxiliary light guide plate  40 , and a second reflecting portion  35 B layered on the entire auxiliary light guide plate-side counter light exit surface  40 D of the auxiliary light guide plate  40 . The reflection sheet  35  also includes a third reflecting portion  35 C laminated along an end face on the outer peripheral side of the curved portion  42  of the auxiliary light guide plate  40  (referred to as a light guide plate-side counter light incident surface  40 B). It is effective to provide the reflection sheet  35  (third reflecting portion  35 C) on the outer peripheral surface (light guide plate-side counter light incident surface  40 B) of the curved portion  42  where an incident angle of light is smaller than the other side surfaces of the auxiliary light guide plate  40  and total reflection hardly occurs. In the present embodiment, these reflecting portions  35 A,  35 B, and  35 C are separated, and each reflecting portion is attached to the light guide plate  25  and the auxiliary light guide plate  40  (see  FIG. 3 ). 
     Note that the reflection sheet  35  is made of a synthetic resin material with at least a reflective surface having excellent light reflectivity, and is capable of efficiently reflecting light that propagates through the light guide plate  25  and escapes from the counter light exit surface  25 D, the auxiliary light guide plate-side counter light exit surface  40 D, and the light guide plate-side counter light incident surface  40 B toward to light guide plate  25  or the auxiliary light guide plate  40 . 
     The LED substrate, the light guide plate  25 , the auxiliary light guide plate  40 , the optical sheet  30 , the reflection sheet  35 , and the like described above are integrated with the liquid crystal panel  11  by, for example, a fixing member such as a double-sided tape and a light-transmissive adhesive to form the liquid crystal display device  10 . 
     The liquid crystal display device  10  according to the present embodiment is configured as described above, and next, the effect will be described. 
     The backlight device  20  according to the present embodiment includes the LED  21  and the light guide plate  25  configured to guide light from the LED  21 , wherein the light guide plate  25  includes a light incident surface  25 A on which the light from the LED  21  is incident, a counter light incident surface  25 B opposite to the light incident surface  25 A, a light exit surface  25 C that is one of a pair of plate surfaces and outputs the light, and a counter light exit surface  25 D opposite to the light exit surface  25 C, and is provided with the light guide plate through-hole  26  (one example of the cutout portion), at least one of the pair of plate surfaces of the light guide plate  25  is provided with the auxiliary light guide plate  40 , the auxiliary light guide plate  40  being configured with a plate-shaped member extending from the light incident surface  25 A to the obscured portion  27  (a region between the light guide plate through-hole  26  and the counter light incident surface  25 B), the auxiliary light guide plate-side light incident surface  40 A, among the end faces of the auxiliary light guide plate  40 , disposed on the light incident surface  25 A side is provided with the auxiliary LED  45 , the auxiliary LED  45  being configured to emit light toward the auxiliary light guide plate-side light incident surface  40 A, and a region, of the auxiliary light guide plate  40 , overlapping the obscured portion  27  of the light guide plate  25  is the light exit section  44 , the light exit section  44  being configured to output light from the auxiliary LED  45  toward the obscured portion  27 . 
     According to such a configuration, even when light that is incident on the light incident surface  25 A of the light guide plate  25  and guided inside the light guide plate  25  is blocked on an optical path thereof by the light guide plate through-hole  26 , the obscured portion  27  is selectively illuminated by locally outputting, from the light exit section  44 , light that is independently guided by the auxiliary light guide plate  40 . Thus, the brightness of the obscured portion  27  is improved, and the brightness unevenness of the backlight device  20  and the liquid crystal display device  10  can be suppressed. 
     Further, in the backlight device  20  according to the present embodiment, the auxiliary light guide plate  40  is disposed to overlap the counter light exit surface  25 D of the light guide plate  25 . 
     According to such a configuration, the light locally output from the light exit section  44  of the auxiliary light guide plate  40  passes through the light guide plate  25  and is output from the light exit surface  25 C of the light guide plate  25 . As a result, compared to a configuration in which the auxiliary light guide plate  40  is disposed to overlap the light exit surface  25 C side of the light guide plate  25 , a boundary between the light guide plate  25  and the auxiliary light guide plate  40  is difficult to distinguish when viewed from the light exit surface  25 C side, and more uniform light is output, and therefore, the brightness unevenness can be further suppressed. 
     The light incident surface  25 A of the light guide plate  25  and the auxiliary light guide plate-side light incident surface  40 A of the auxiliary light guide plate  40  are disposed to be overlapped with each other. According to such a configuration, the LED  21  and the auxiliary LED  45  can be collectively disposed in a state of being overlaid with each other on one side of the light guide plate  25  and the auxiliary light guide plate  40 , and thus, a simple configuration can be achieved. 
     The auxiliary light guide plate  40  is disposed to entirely overlap the light guide plate  25 . According to such a configuration, the auxiliary light guide plate  40  does not protrude in a plate surface direction from the light guide plate  25 , and thus a cutout portion such as the light guide plate through-hole  26  provided in the light guide plate  25  can be utilized. 
     The light guide plate  25  is provided with the light guide plate through-hole  26 , the auxiliary light guide plate  40  is formed into a U-shape including the pair of linear portions  41  and the curved portion  42 , the pair of linear portions  41  being disposed to extend linearly from the light incident surface  25 A to lateral side portions of the light guide plate through-hole  26 , the curved portion  42  being curved to wrap around the light guide plate through-hole  26  inward continuously from the linear portions  41 . According to such a configuration, the obscured portion  27  can be efficiently radiated with the light from the auxiliary LED  45  by the auxiliary light guide plate  40 . 
     The reflection sheet  35  (third reflecting portion  35 C) that reflects light is provided on the light guide plate-side counter light incident surface  40 B that is the outer peripheral end face of the curved portion  42 . According to such a configuration, light escaping from the curved portion  42  where an incident angle of light is smaller than the other side surfaces of the auxiliary light guide plate  40  and total reflection hardly occurs can be efficiently returned to the auxiliary light guide plate  40 . 
     The liquid crystal display device  10  according to the present embodiment includes the liquid crystal panel  11  and the backlight device  20  described above. The liquid crystal panel  11  includes the panel through-hole  12  that penetrates the plate surface at a position corresponding to the light guide plate through-hole  26 . 
     According to the liquid crystal display device  10  and the backlight device  20  described above according to the present embodiment, the brightness unevenness can be suppressed even in a case that the through-holes  12  and  26  are provided in the liquid crystal panel  11  and the light guide plate  25 . 
     Second Embodiment 
     Next, the second embodiment will be described with reference to  FIGS. 7 and 8 . A liquid crystal display device and a backlight device according to the present embodiment differ from the first embodiment described above in a position and shape of a cutout portion provided in a light guide plate  55 . Hereinafter, a configuration different from the first embodiment will be described, and similar configurations are assigned with reference signs obtained by adding 30 to the reference signs in the first embodiment and descriptions thereof will be omitted. 
     The light guide plate  55  used in the present embodiment differs from the first embodiment in that, instead of the light guide plate through-hole  26  of the first embodiment, a narrowed portion  56  (one example of the cutout portion and the recessed portion) is provided that is formed by cutting out substantially entirely each of end edge portions on long sides of the light guide plate  55  constituting a pair of side surface  55 E into a flattened U-shape. The pair of narrowed portions  56  are axisymmetric with respect to a long side direction (Y-axis direction) of the light guide plate  55 . 
     According to such a configuration, a portion of the light having directionality incident on the light guide plate  55  from a light incident surface  55 A is blocked on an optical path thereof by a member disposed in the narrowed portion  56  or the narrowed portion  56  itself. Thus, a region between the narrowed portions  56  and a counter light incident surface  55 B is an obscured portion  57  where is not easily reached by light. The obscured portion  57  generates a brightness unevenness in the backlight device. 
     Therefore, the light guide plate  55  according to the present embodiment is integrally provided with an auxiliary light guide plate  70  extending from the light incident surface  55 A to the obscured portion  57  similarly to the above-described embodiment. The auxiliary light guide plate  70  according to the present embodiment is generally formed into a Y-shape, and includes a linear portion  71  and a pair of branch portions  72 , the linear portion  71  extending from the center of the light incident surface  55 A of the light guide plate  55  in the width direction (X-axis direction) toward the counter light incident surface  55 B, the pair of branch portions  72  extending along the edge portions of the pair of narrowed portions  56  on the counter light incident surface  55 B side. The outer peripheral edge of each branch portion  72  is configured to coincide with a side edge on the counter light incident surface  55 B side of the narrowed portion  56 . With such a configuration, a portion of each branch portion  72  of the auxiliary light guide plate  70  is in a state of being overlaid on a region of the obscured portion  57  adjacent to the narrowed portion  56 . 
     Among end faces of the auxiliary light guide plate  70  formed into a Y-shape, an end face overlaid with the light incident surface  55 A of the light guide plate  55  is an auxiliary light guide plate-side light incident surface  70 A, and an auxiliary LED  75  that emits light toward the auxiliary light guide plate  70  is disposed to face the auxiliary light guide plate-side light incident surface  70 A. In other words, the light incident surfaces  55 A and  70 A of the light guide plate  55  and the auxiliary light guide plate  70 , respectively, are overlaid with each other to face the same direction, and the LED  61  and the auxiliary LED  75  can be collectively disposed in a state of being overlaid with each other on one side of the light guide plate  55  and the auxiliary light guide plate  70 . 
     Furthermore, a region, in a lower face of the auxiliary light guide plate  70  (referred to as an auxiliary light guide plate-side counter light exit surface  70 D) of the auxiliary light guide plate  70 , that overlaps the obscured portion  57  in a state in which the auxiliary light guide plate  70  is overlaid on the light guide plate  55  is a light exit section  74  provided with an uneven pattern having a plurality of lenticular protrusions protruding toward the rear side. With such a configuration, the auxiliary light guide plate  70  introduces light from the auxiliary LED  75  through the auxiliary light guide plate-side light incident surface  70 A and propagates the light therein, and thereafter, raises the light by the light exit section  74  up along the Z-axis direction to output the light toward the front side (the liquid crystal panel  11  side). 
     Note that in the present embodiment as well, similar to the embodiment described above, the reflective sheet is disposed on the entire rear face of the light guide plate  55  including the auxiliary light guide plate  70 . 
     According to the embodiment like this as well, similar to the first embodiment described above, even in a case that light that is incident on the light incident surface  55 A of the light guide plate  55  and guided inside the light guide plate  55  is blocked on an optical path thereof by the narrowed portions  56 , the obscured portion  57  is illuminated by light selectively output from the light exit section  74  of the auxiliary light guide plate  70 , and therefore, the brightness unevenness can be suppressed. 
     Other Embodiments 
     The technique disclosed herein is not limited to the embodiments described above and illustrated by the drawings, and embodiments such as those described below are also included within the technical scope of the present disclosure. 
     (1) In the embodiments described above, the example has been given of a planar liquid crystal display device including the light guide plate through-hole  26  and the narrowed portion  56 . However, the technique disclosed herein can also be applied to a display device having a curved surface shape, a display device provided with two or more through-holes, or a display device having a shape different from those described above. 
     (2) The form of the auxiliary light guide plates  40  and  70  are not limited to the embodiments described above. In other words, the auxiliary light guide plate  40  or  70  may have any form as long as the auxiliary light guide plate  40  or  70  is provided with the light exit section  44  or  74  that outputs light to at least a portion of the obscured portion  27  or  57 . 
     (3) In the embodiment described above, the configuration is illustrated in which the auxiliary light guide plates  40  and  70  are overlaid on portions of the obscured portions  27  and  57 , respectively, but the auxiliary light guide plates  40  and  70  may be configured to be overlaid on the entire obscured portions. In this case, it is possible to adjust the intensity of the emission light by changing the uneven pattern in accordance with the brightness of the region in the obscured portion. 
     (4) The auxiliary light guide plate may not be entirely overlaid on the light guide plate. That is, a configuration that the auxiliary light guide plate is disposed to protrude from the light guide plate is included in the technical scope disclosed herein. 
     (5) In the embodiments described above, the LEDs  21  and  61  of the light guide plates  25  and  55 , and the auxiliary LEDs  45  and  75  of the auxiliary light guide plates  40  and  70  are provided separately. However, the LED and the auxiliary LED may be the same. That is, a large LED that spans the light incident surfaces of both the light guide plate and the auxiliary light guide plate may be used at the position where the auxiliary light guide plate is disposed. 
     (6) In the embodiments described above, the configuration is illustrated in which the auxiliary light guide plates  40  and  70  are overlaid on the counter light exit surfaces  25 D and  55 D of the light guide plates  25  and  55 . However, the auxiliary light guide plate may be configured to be overlaid on the light exit surface. The auxiliary light guide plate may also be overlaid on both surfaces. 
     (7) The light incident surface of the light guide plate and the light incident surface of the auxiliary light guide plate need not necessarily be disposed to be overlapped with each other. 
     (8) An emission pattern of the light exit section is not limited to a lenticular protrusion. For example, the pattern may have a rough surface or a prismatic shape, or in other words, may have a shape having a function of outputting light toward the obscured portion. 
     (9) In the embodiments described above, the configuration is illustrated in which the reflection sheet  35  is divided and applied to the light guide plate  25  (excluding the region where the auxiliary light guide plate is disposed) and the rear face of the auxiliary light guide plate  40  (counter light exit surfaces  25 D,  40 D). However, as illustrated in  FIG. 9 , a reflection sheet  80  may be configured to cover the entire light guide plate  25  and the auxiliary light guide plate  40  with a single sheet. In this case, the counter light exit surface  25 D and the reflection sheet  80  may be disposed in a separated state. 
     (10) In the first embodiment described above, the auxiliary light guide plate  40  is constituted with the pair of linear portions  41  and the curved portion  42 . However, the curved portion may be a bending portion in a shape obtained by bending a straight line.