Abstract:
A backlight unit is provided which includes: a light guide plate which guides incident light from a lateral side of the light guide plate toward a liquid crystal display (LCD) panel placed in front of the light guide plate; a light source unit which includes a light source which emits the light and a light source supporting member which supports the light source and is arranged adjacent to the lateral side of the light guide plate; a supporting frame which is arranged in the backlight unit; a quantum dot (QD) bar which is arranged between the lateral side of the light guide plate and the light source and changes a color of the light emitted from the light source; and a QD-bar fastening unit which fastens the QD bar to at least one of the light source supporting member and the supporting frame.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority from Korean Patent Application No. 10-2011-0085525, filed on Aug. 26, 2011 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND 
     1. Field 
     Apparatuses and methods consistent with the exemplary embodiments relate to a liquid crystal display (LCD) device, and more particularly, to a backlight unit employing a quantum dot (QD) bar and a light emitting diode (LED) as a light source, a manufacturing method thereof, and an LCD device having the same. 
     2. Description of the Related Art 
     A backlight unit for an LCD device includes light emitting diodes  10  arranged along a lateral side of a light guide plate  20  as shown in  FIG. 18 . Light emitted from the LED  10  enters the lateral sides of the light guide plate  20 , propagates to the center of the light guide plate  20  by total reflection, and exits the light guide plate  20  through a front patterned surface, thereby materializing a surface light source. 
     Usually, white LEDs emitting monochromatic light have been used as the LEDs  10  arranged along the lateral sides of the backlight unit. The white LEDs generally emit white light by using a Blue-chip along with green and red phosphors. 
     The LEDs  10  used in the related art backlight unit employs a single LED package that emits one color, and therefore their color reproduction is just 75% of a national television system committee (NTSC) area. Also, the color reproduction, efficiency and white coordinate of a panel is susceptible to matching between a peak wavelength of three colors, red, green and blue (R, G, B), of the white LED and a peak wavelength of a color filter for the liquid crystal of the LCD device. 
     To make up for deterioration in the color reproduction of the white LED used in the related art backlight unit, there has been proposed technology of using a blue LED  10  instead of the white LED and a quantum dot (QB) bar  30  as a light source of the backlight unit, disclosed in Korean Patent Publications No. 10-2011-0068110 and No. 10-2011-0012246. 
     As shown in  FIG. 19 , the QD bar  30  is adhered between the blue LED  10  and the light guide plate  20  by a transparent optical resin layer or an adhesive layer  40 ,  50 . However, it is very inconvenient to use the optical resin layer or the adhesive layer  40 ,  50  in the adhesion for the QD bar  30 , and thus productivity decreases. Further, the optical resin layer or the adhesive may distort the light emitted from the LED and the QD bar. 
     Also, heat generated by the LED is transferred to the light guide plate  20  via the optical resin layer or the adhesive layer, and therefore the light guide plate  20  is twisted, thereby having an effect on the adhered QD bar  30  which damages the QD bar  30 . 
     SUMMARY 
     Accordingly, one or more exemplary embodiments provide a backlight unit which is excellent in color reproduction, and an LCD device having the same. 
     Another exemplary embodiment is to provide a backlight unit having a structure in which heat generated from an LED is not transferred to a light guide plate, and an LCD device having the same. 
     Still another exemplary embodiment is to provide a backlight unit to which a QD bar can be easily fastened, and a manufacturing method thereof. 
     Yet another exemplary embodiment is to provide a backlight unit having a structure for improving workability and increasing productivity, and a manufacturing method thereof. 
     Still another exemplary embodiment is to provide a backlight unit having a structure in which light emitted by an LED is transferred to a light guide plate without distortion, and an LCD device having the same. 
     The foregoing and/or other aspects may be achieved by providing a backlight unit including: a light guide plate which guides incident light from a lateral side of the light guide plate toward a liquid crystal display (LCD) panel placed in front of the light guide plate; a light source unit which comprises a light source which emits the light and a light source supporting member which supports the light source and is arranged adjacent to the lateral side of the light guide plate; a supporting frame which is arranged in the backlight unit; a quantum dot (QD) bar which is arranged between the lateral side of the light guide plate and the light source and changes a color of the light emitted from the light source; and a QD-bar fastening unit which fastens the QD bar to at least one of the light source supporting member and the supporting frame. 
     The QD bar may be spaced apart from at least one of the light guide plate and the light source. 
     The light source may include a blue light emitting diode (LED). 
     The light source supporting member may include a printed circuit board (PCB) mounted with the light source. 
     The supporting frame may include at least one of a heat sinking plate which radiates heat from the light source, a light guide plate supporting frame which supports the light guide plate, and a middle molding part which extends along a lateral end of the backlight unit, between a front and a rear of the backlight unit. 
     The at least one of the heat sinking plate, the light guide plate, and the middle molding part comprises a bending end part which extends from the lateral end of the backlight unit toward the lateral side of the light guide plate. 
     The QD-bar fastening unit may include an adhesive. 
     The QD-bar fastening unit may include a groove which is formed in at least one of the light source supporting member and the supporting frame and to which the QD bar is fitted therein. 
     The QD-bar fastening unit may include a connecting member which connects the QD bar to the light source supporting member. 
     The connecting member fastens the QD bar to the light source supporting member such that the QD bar is separated from the light source supporting member so that the light source is accommodated between the light source supporting member and the QD bar. 
     The QD-bar fastening unit may include a fastening pin coupled to the QD bar; and a socket provided on at least one of the light source supporting member and the supporting frame, and is coupled to the fastening pin. 
     The QD-bar fastening unit may include a socket coupled to the QD bar; and a fastening pin provided in at least one of the light source supporting member and the supporting frame, and is coupled to the socket. 
     The QD-bar fastening unit may include a fastening pin which is coupled to the QD bar and has an elastic projection; and a fastening part which is provided in at least one of the light source supporting member and the supporting frame, and which accommodates and is coupled to the elastic projection. 
     The QD-bar fastening unit may include a fastening pin which is provided in at least one of the light source supporting member and the supporting frame, and which has an elastic projection; and a fastening part which is coupled to the QD bar, and which accommodates and is coupled to the elastic projection. 
     The QD-bar fastening unit may include a bolt which is coupled to the QD bar; and a welding part which couples at least one of the light source supporting member and the supporting frame to the fastening pin. 
     The QD-bar fastening unit may include a fastening pin which is coupled to the QD bar; and a welding part which couples at least one of the light source supporting member and the supporting frame to the fastening pin. 
     The QD-bar fastening unit may include a groove formed at a lateral end of the backlight unit and which receives the QD bar inserted therein. 
     Another aspect may be achieved by providing a backlight unit including: a light guide plate which guides incident light from a lateral side of the light guide plate toward a liquid crystal display (LCD) panel placed in front of the light guide plate; a light source unit which comprises a light source which emits the light and a light source supporting member which supports the light source and is arranged adjacent to the lateral side of the light guide plate; a quantum dot (QD) bar which is arranged between the lateral side of the light guide plate and the light source and changes a color of the light emitted from the light source; and a pressing member which is fastened while pressing the QD bar toward the lateral side of the light guide plate. 
     The pressing member may include at least one of a light source supporting frame, a heat sinking plate which radiates heat from the light source, a light guide plate supporting frame which supports the light guide plate, and a middle molding part which extends along a lateral end of the backlight unit, between a front and a rear of the backlight unit. 
     Still another aspect may be achieved by providing a method of manufacturing a backlight unit, the method including arranging a light guide plate behind a liquid crystal display (LCD) panel; preparing a light source unit by arranging a light source onto a light source supporting member and fastening a quantum dot (QD) bar to the light source supporting member; arranging the light source unit to a lateral side of the light guide plate so that the QD bar is arranged between the light source and the light guide plate; and fastening the light source unit to a supporting frame arranged in the backlight unit. 
     The supporting frame may include at least one of a heat sinking plate which radiates heat from the light source, a light guide plate supporting frame which supports the light guide plate, and a middle molding part which extends along a lateral end of the backlight unit, between a front and a rear of the backlight unit. 
     Yet another aspect may be achieved by providing a method of manufacturing a backlight unit, the method including arranging a light guide plate behind a liquid crystal display (LCD) panel; arranging a quantum dot (QD) bar at a lateral side of the light guide plate; arranging a light source unit comprising a light source such that the QD bar is arranged between the light source and the light guide plate; pressing the QD bar toward the lateral side of the light guide plate by a pressing member so that the QD bar is adhered to the lateral side of the light guide plate; and fastening the pressing member to a supporting frame arranged in the backlight unit. 
     The pressing member may include at least one of a light source supporting frame which supports the light source, a heat sinking plate which radiates heat from the light source, a light guide plate supporting frame which supports the light guide plate, and a middle molding part which extends along a lateral end of the backlight unit, between a front and a rear of the backlight unit. 
     The pressing member may include a QD-bar guide groove extended in a direction perpendicular to the lateral side of the light guide plate. 
     The pressing member may include a QD-bar guide groove extended in a lengthwise direction of the QD bar. 
     Still another aspect may be achieved by providing a liquid crystal display (LCD) device including the foregoing backlight unit; and a LCD panel which comprises a liquid crystal layer, a thin film transistor layer arranged between the liquid crystal layer and the light guide plate of the backlight unit and which controls light passing through the liquid crystal layer, and a color filter layer which materializes color of light passed through the liquid crystal layer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and/or other aspects will become apparent and more readily appreciated from the following description of the exemplary embodiments, taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a schematic view of an LCD device having a backlight unit according to a first exemplary embodiment; 
         FIG. 2  is a schematic view of an LCD device having a backlight unit according to a second exemplary embodiment; 
         FIG. 3  is a schematic view of an LCD device having a backlight unit according to a third exemplary embodiment; 
         FIGS. 4A and 4B  are schematic views of an LCD device having a backlight unit according to a fourth exemplary embodiment; 
         FIG. 5  is a view showing a QD bar with a fastening pin according to an exemplary embodiment; 
         FIG. 6  is a schematic view of an LCD device having a backlight unit employing the QD bar shown in  FIG. 5  according to a fifth exemplary embodiment; 
         FIG. 7  is a schematic view of an LCD device having a backlight unit according to a sixth exemplary embodiment; 
         FIG. 8  is a view showing a QD bar with another fastening pin according to an exemplary embodiment; 
         FIG. 9  is a schematic view of an LCD device having a backlight unit employing the QD bar shown in  FIG. 8  according to a seventh exemplary embodiment; 
         FIG. 10  is a schematic view of an LCD device having a backlight unit employing the QD bar shown in  FIG. 8  according to an eighth exemplary embodiment; 
         FIG. 11  is a schematic view of an LCD device having a backlight unit employing the QD bar shown in  FIG. 8  according to a ninth exemplary embodiment; 
         FIG. 12  is a schematic view of an LCD device having a backlight unit according to a tenth exemplary embodiment; 
         FIG. 13  is a schematic view of an LCD device having a backlight unit according to an eleventh exemplary embodiment; 
         FIGS. 14A and 14B  are schematic views of an LCD device having a backlight unit and a light guide plate according to a twelfth exemplary embodiment; 
         FIG. 15  is a schematic view of an LCD device having a backlight unit according to a thirteenth exemplary embodiment; 
         FIGS. 16(   a ) to  16 ( d ) are a process view of a manufacturing method of a backlight unit according to an exemplary embodiment; 
         FIGS. 17(   a ) to  17 ( e ) are a process view of a manufacturing method of a backlight unit according to another exemplary embodiment; 
         FIG. 18  is a schematic view of major parts taken from a related backlight unit; and 
         FIG. 19  is a schematic view of major parts taken from a related art backlight unit. 
     
    
    
     DETAILED DESCRIPTION 
     Below, exemplary embodiments will be described in detail with reference to accompanying drawings. For the convenience of description, elements having no direct relationship to the exemplary embodiments are omitted for clarity, and like reference numerals refer to like elements throughout. Here, the “rear” refers to a direction where a light guide plate  120  is placed in an LCD panel  110 , and the “up,” “down,” “left” and “right” are defined with respect to the front of the LCD panel  110 . 
     As shown in  FIG. 1 , an LCD device  100  includes an LCD panel  110  and a backlight unit. The backlight unit includes a dual brightness enhance film (DBEF) sheet  112 , a prism sheet  114 , a diffuser sheet  116 , a light guide plate  120 , a reflection sheet  122 , an LED  130  and a QD bar  140  arranged in sequence on the rear of the LCD panel  110 . 
     In the LCD panel  110 , a nematic liquid crystal is interposed between two sheets of glass, and counter electrodes with a thin film transistor are arranged on the two sheets of glass. An electric field applied to the counter electrodes changes a twisted angle of a liquid crystal material interposed between the glass substrates, and adjusts penetration of light emitted from the rear. 
     The DBEF sheet  112  serves to reduce loss of light exiting from the prism sheet  114  to be described later. 
     The prism sheet  114  changes side light into front light with regard to the light passed through the diffuser sheet  116  to be described later, and concentrates radiated light, thereby increasing brightness. 
     The diffuser sheet  116  serves to diffuse the light exiting the light guide plate  120  and make the light uniform. For example, the diffuser sheet  116  may be made of polyester or polycarbonate. 
     The light guide plate  120  serves to make the light entered from LED  130  be materialized into uniform surface light. For example, the light guide plate  120  may be made of an acrylic mold. 
     The reflection sheet  122  is placed behind the light guide plate  120 , and reflects light scattered from the light guide plate  120 , the DBEF sheet  112 , the prism sheet  114  and the diffuser sheet  116  toward the front of the LCD device  100 . 
     The LED  130  is placed at lateral sides of the light guide plate  120  while being attached to a printed circuit board  129 . The LED  130  may employ a blue LED. 
     The backlight unit as shown in  FIG. 1  is not a direct type where the light source unit  129 ,  130  is placed behind the light guide plate  120  but an edge type where the light source unit  129 ,  130  is placed at the sides of the light guide plate  120 . Also, the light source unit  129 ,  130  is a side-view type where the printed circuit board  129  is parallel with the light guide plate  120  and the light is emitted at a side to the light guide plate  120 . 
     The QD bar  140  is arranged between the LED  130  and the side of the light guide plate  120  and is a bar in which quantum dot fluorescent substance is injected. The quantum dot is a particle that generates fluorescent light that is much stronger than that of a general fluorescent material within a narrow wavelength range and forms a core with nano-sized II-IV semiconductor particles (e.g., CdSe, CdTe, CdS, etc). 
     For example, the QD bar  140  is arranged between the blue LED  130  and the light guide plate  120  and serves to convert blue light from the blue LED  130  into white light. 
     As shown in  FIG. 16(   b ), the QD bar  140  in this exemplary embodiment is adhered to the printed circuit board  129  supporting the LED  130  by an adhesive. Since the QD bar  140  is attached to the printed circuit board  129  that is a light source supporting member for supporting the LED  130 , it can be conveniently and easily fastened thereto. That is, as shown in  FIG. 16(   c ), a manufacturing work is simple because the QD bar  140  together with the LED  130  is attached to the printed circuit board  129  and then the QD bar  140  and the LED  130  are arranged adjacent to each other in a proximity of a lateral side of the light guide plate  120 . 
     Also, if the QD bar  140  is fastened as described above, there is no medium such as an adhesive between the LED  130  and the QD bar  140  and between the QD bar  140  and the light guide plate  120 , and therefore there is no distortion of light. 
     The QD bar  140  may be arranged respectively leaving spaces L 1  and L 2  (i.e., air gaps) from the LED  130  and the light guide plate  120 . Thus, if the QD bar  140  is spaced apart from the LED  130  and from the light guide plate  120 , heat generated from the LED  130  cannot be transferred to the light guide plate  120 . 
     Below, operations of a backlight unit according to a first exemplary embodiment will be described with reference to  FIG. 1 . 
     The blue light emitted from the blue LED  130  is converted into the white light while passing through the adjacent QD bar  140 , and enters the lateral side of the light guide plate  120  that is adjacent to the LED  130 /QD bar  140  assembly. The light entering the lateral side of the light guide plate  120  exits the light guide plate  20  through a front patterned surface thereof, thereby materializing a surface light source. Surface light is transferred to the LCD panel  110  via the diffuser sheet  116 , the prism sheet  114  and the DBEF sheet  112 . 
       FIG. 2  is a schematic view of an LCD device having a backlight unit according to a second exemplary embodiment. The QD bar  140  is placed between the LED  130  and the light guide plate  120 . In this exemplary embodiment, the QD bar  140  is fastened to a heat sinking plate  125  arranged on the rear of the printed circuit board  129  used as a light source supporting member. Furthermore, the heat sinking plate  125  extends along the rear of the light guide plate  120  and the reflection sheet  122 . Here, the heat sinking plate  125  is to radiate heat from the LED  130 . 
     As shown in  FIG. 2 , the heat sink  125  to which the QD bar  140  is fastened includes a main body part  125 - 1  which extends past the lateral side of the light guide plate  120  toward an outskirt supporting frame  128  and in parallel with the rear of the light guide plate  120 , an erect part  125 - 2  bent from the main body part which extends in parallel with the lateral side of the light guide plate  120 , and a bending end part  125 - 3  which is bent from the erect part, extends toward the light guide plate  120  in parallel to the main body part, and is spaced apart from the main body part by a length of the erect part. 
     A space formed by the main body part  125 - 1 , the erect part  125 - 2  and the bending end part  125 - 3  of the heat sinking plate  125  accommodates the light source  130 , the light source supporting member  129  and the QD bar  140 . 
     The bending end part  125 - 3  and the main body part  125 - 1  of the heat sinking plate  125  are opposite to each other, and the opposite parts are respectively formed with grooves  127 - 1  as a QD-bar fastening unit. The QD bar  140  may be fitted into and fastened to the grooves  127 - 1  opposite to each other. The above fastening method of fitting the QD bar  140  into the grooves  127 - 1  of the heat sinking plate  125  is nothing but an example. Alternatively, the QD bar  140  may be supported on the heat sinking plate  125  by various methods. The groove  127 - 1  of the heat sinking plate  125  may be provided in either of the bending end part  125 - 3  or the main body part  125 - 1 . 
     According to the second exemplary embodiment, the QD bar  140 , the light source unit  129 ,  130  and the heat sinking plate  125  are assembled as a single body, and it is thus convenient and easy to arrange them adjacent to the lateral side of the light guide plate  120 . Alternatively, the QD bar  140  may be fastened after previously arranging the light source unit  129 ,  130  to the lateral side of the light guide plate  120 . The QD bar  140  is arranged within the assembly such that spaces (i.e., air gaps) are present between itself and the LED  130  and itself and the light guide plate  120 . 
     The light source unit  129 ,  130  shown in  FIG. 2  is a top-view type where the printed circuit board  129  used as the light source supporting member is arranged in parallel with the lateral side of the light guide plate  120 . The printed circuit board  129  may be supported by the erect part  125 - 2  of the heat sinking plate  125 . Of course, the light source unit  129 ,  130  the side-view type may be used as shown in  FIG. 1 . 
       FIG. 3  is a schematic view of an LCD device having a backlight unit according to a third exemplary embodiment. The QD bar  140  may be fastened to the heat sinking plate  125  and a light guide plate supporting frame  124 . 
     The light guide plate supporting frame  124  may include a main body part  124 - 1  that is parallel with the rear of the light guide plate  120  and extends past of the lateral side of the light guide plate  120  toward an outskirt supporting frame  128 , an erect part  124 - 2  that is bent from the main body part  124 - 1  and extends in parallel with the lateral side of the light guide plate  120 , and a bending end part  124 - 3  that is bent from the erect part  124 - 2  and extends toward the light guide plate  120 . 
     The heat sinking plate  125  is placed behind the light guide plate  120  and arranged between the light guide plate  120  and the light guide plate supporting frame  124 . At least a main body part  125 - 1  of the heat sinking plate  125  is opposite to the bending end part  124 - 3  of the light guide plate supporting frame  124 , and an erect part  125 - 2  of the heat sinking plate  125  is disposed between the erect part  124 - 2  of the light guide plate supporting frame  124  and the light source supporting member  129 . 
     The bending end part  124 - 3  of light guide plate supporting frame  124  and the main body part  125 - 1  of the heat sinking plate  125 , which are opposite to each other, include a groove  127 - 2  as the QD-bar fastening unit into which the QD bar  140  can be fitted. If the heat sinking plate  125  has no part opposite to the bending end part  124 - 3  of the light guide plate supporting frame  124  or there is no heat sinking plate  125 , the groove  127 - 2  may be provided in the main body part  124 - 1  of the light guide plate supporting frame  124 . The groove  127 - 2  to which the QD bar  140  is fitted may be provided in either of the bending end part  124 - 2  of the light guide plate supporting frame  124  or the heat sinking plate  125 . 
     According to the third exemplary embodiment, the QD bar  140  may be provided in the light guide plate  120  as being previously manufactured together with the light source unit  129 ,  130 , the heat sinking plate  125  and the light guide plate supporting plate  124 . Also, the QD bar  140  may be fitted to the groove  127 - 2  provided in at least one of the heat sinking plate  125  and the light guide plate supporting frame after the light source unit  129 ,  130 , the heat sinking plate  125  and the light guide plate supporting frame  124  are first arranged on the lateral side of the light guide plate  120 . 
       FIGS. 4A and 4B  are schematic views of an LCD device having a backlight unit according to a fourth exemplary embodiment. The QD bar  140  may be fastened to a light source supporting member  129  supporting the LED  130  by a connecting members  142  (only one shown) attached as a fastening means to the opposite ends of the QD bar  140 . The connecting members  142  may be attached to the QD bar  140  by an adhesive, and may be attached to other sides of the QD bar  140  as well as the opposite ends. 
     The QD bar  140  may be fastened to the heat sinking plate  125  or the light guide plate supporting frame  124  instead of being fasted to the light source supporting member  129 . 
       FIGS. 5 and 6  are schematic views of a backlight unit according to a fifth exemplary embodiment. As shown in  FIG. 5 , the backlight unit may include a fastening pins  141  attached as the QD-bar fastening unit to the opposite ends of the QD bar  140  and which extend lengthwise. The supporting frame adjacent to the opposite ends of the QD bar  140 , i.e., the supporting frame arranged on the top and bottom sides adjacent to the lateral sides of the light guide plate where the light source unit  129 ,  130  is placed is attached with a socket  150 - 1 , or other type of receptacle, to which the fastening pin  141  is fitted. The socket  150 - 1  is provided in the form of a receptacle and internally includes two engaged elastic pieces. Alternatively, the socket  150 - 1  may have various coupling structures such as a latch lock, etc. 
     The fastening pin  141  may be fitted into the socket  150 - 1  in a lengthwise direction of the QD bar  140 . At this time, it may be difficult to insert the fastening pin  141  in the lengthwise direction if an inner space is narrow. Thus, the fastening pin  141  may be inserted in the socket  150 - 1  in a direction of penetrating into or out of the drawings. If the socket&#39;s mouth for the fastening pin is differently arranged, the QD bar  140  may be inserted in a direction perpendicular to the lengthwise direction. 
       FIG. 7  is a schematic view of a backlight unit according to a sixth exemplary embodiment. The QD bar  140  is provided with a fastening pin  141  extended perpendicularly to the lengthwise direction at one side 
     Adjacent to the lateral side of the light guide plate  120 , the light source unit  129 ,  130 , the heat sinking plate  125 , the light guide plate supporting frame  124 , a middle molding unit  126 , and an outskirt supporting frame  128  are arranged in sequence. 
     Each of the middle molding unit  126  and the outskirt supporting frame  128  includes a lateral part which extends in parallel with the lateral side of the light guide plate  120 , and a front part bent from the lateral part and which extends toward the light guide plate  120  in parallel with the light guide plate  120 . As shown in  FIG. 7 , the LCD panel  110  is secured by being fitted between the front part of the middle molding unit  126  and the front part of the outskirt supporting frame  128 . 
     The front part of the middle molding unit  126  is internally attached with a receptacle socket  153  to which the fastening pin  141  is fitted. 
     The fastening pin  141  may be fitted to the socket  153  in a lengthwise direction of the fastening fin  141 , i.e., in a direction from bottom to top as seen from the drawings. At this time, it may be difficult to insert the fastening pin  141  if an inner space is narrow. Thus, the fastening pin  141  may be inserted in the socket  150 - 1  in a direction of penetrating the drawings. If the socket&#39;s mouth for the fastening pin  141  is differently arranged, the QD bar  140  may be inserted in a direction perpendicular to the lengthwise direction. 
     The heat sinking plate  125  is positioned opposite to the socket  153  and may be provided with the groove  127 - 2 . 
     One side of the QD bar  140  may be fastened by fitting the fastening pin  141  to the socket arranged in the front part of the middle molding unit  126 , and the other side may be fastened by fitting the QD bar  140  itself to the groove  127 - 2  of the heat sinking plate  125 . Alternatively, the QD bar  140  may be fastened by only coupling between the fastening pin  141  and the socket  153 . Also, the QD bar  140  may be fastened by only fitting the other side to the groove  127 - 2  of the heat sinking plate  125 . 
       FIG. 8  is a view showing the QD bar  140  of  FIG. 5  with another fastening pin  141  according to an exemplary embodiment, in which the fastening pin  141  may include an elastic projection  144 . 
       FIG. 9  is a schematic view of a backlight unit according to a seventh exemplary embodiment. The fastening pin  141  attached to the QD bar  140  includes the elastic projection  144  shown in  FIG. 8 , and may be fitted to the socket  153  attached to the front part of the middle molding unit  126 . Such a structure makes the QD bar  140  be more firmly fastened. Accordingly, it is possible to stably maintain the fastening of the QD bar  140  without the fitting based on the groove  127 - 2  of the heat sinking plate  125  as described in the sixth exemplary embodiment. 
       FIG. 10  is a schematic view of a backlight unit according to an eighth exemplary embodiment. In this exemplary embodiment, in contrast to the seventh exemplary embodiment, the fastening pin  141  is attached to the front part of the middle molding part  126 , and the socket  153  is attached to the QD bar  140 . 
       FIG. 11  is a schematic view of a backlight unit according to a ninth exemplary embodiment. In this exemplary embodiment, the QD bar  141  is provided with the fastening pin  141  having the elastic projection  144 . 
     The heat sinking plate  125  includes the bending end part  125 - 3  extended toward the light guide plate  120  at the lateral side of the light guide plate  120 . The bending end part  125 - 3  of the heat sinking plate  125  includes a through hole to which the fastening pin  141  is fitted. The through hole may be formed in the bending end part of the light source supporting member  129  which is bent to extend toward the light guide plate  120  at the lateral side of the light guide plate  120 , the bending end part  124 - 3  of the light guide plate supporting frame  124 , and the bending end part of the middle molding part  126  as well as that of the heat sinking plate  125 . 
       FIG. 12  is a schematic view of a backlight unit according to a tenth exemplary embodiment. In this exemplary embodiment, the QD bar  141  is provided with the fastening pin  141  having a bolt  143 . The light guide plate supporting frame  124  includes the bending end part  124 - 3  which extends toward the light guide plate  120  at the lateral side of the light guide plate  120 . The bending end part  124 - 3  of the light guide plate supporting frame  124  includes a through hole in which the bolt  143  of the fastening pin  131  is inserted. 
     The QD bar  140  may be fastened by inserting and penetrating the bolt  143  of the fastening pin  141  into the through hole of the bending end part of the light guide plate supporting frame  124 , and then fastening the bolt  143  with a nut  152 . 
       FIG. 13  is a schematic view of a backlight unit according to an eleventh exemplary embodiment. In this exemplary embodiment, the QD bar  140  is provided with the fastening pin  141 . The heat sinking plate  125  includes the bending end part  125 - 3  which extends towards the light guide plate  120  at the lateral side of the light guide plate  120 . The fastening pin  141  of the QD bar  140  may be directly soldered or welded to the bending end part  12 - 3  of the heat sinking plate  125 . 
       FIGS. 14A and 14B  are schematic views of a backlight unit according to a twelfth exemplary embodiment. The light guide plate  120  includes a groove  121  at its lateral side, in which the QD bar  140  is inserted. The QD bar  140  itself is fitted and fastened to the groove  121  formed at the lateral side of the light guide plate  120 . 
       FIG. 15  is a schematic view of a backlight unit according to a thirteenth exemplary embodiment. The QD bar  140  is closely adhered and fastened between the light source unit  129 ,  130  and the lateral side of the light guide plate  120 . Below, a method of adhering and fastening the QD bar  140  will be described with reference to  FIG. 17 . 
     First, the heat sinking plate  125  includes the main body part  125 - 1  which is configured to extend past of the lateral side of the light guide plate in parallel with the rear of the light guide plate  120 , the erect part  125 - 2  which is bent from the main body part  125 - 1  and extends in parallel with the lateral side of the light guide plate  120 , and the bending end part  125 - 3  which is bent from the erect part  125 - 2  and extends toward the light guide plate  120  at the lateral side of the light guide plate  120 . At this time, the heat sinking plate  125  may include a predetermined space formed by the main body part  125 - 1 , the erect part  125 - 2  and the bending end part  12 - 3 . Also, the bending end part  125 - 3  and the main body part  125 - 1  of the heat sinking plate  125  may be formed with a QD-bar guide groove  160 . 
     The QD-bar guide groove  160  may be formed to extend in a lengthwise direction of the QD bar, or may be formed to extend in a direction perpendicular to the lengthwise direction of the QD bar as shown in  FIG. 17 . 
     Next, the light source unit  129 ,  130  and the QD bar  140  are sequentially inserted in the predetermined space of the heat sinking plate  125 . At this time, the inserted light source unit  129 ,  130  and heat sinking plate  125  may be adhered and fastened to the heat sinking plate  125  within the predetermined space by an adhesive. 
     Then, the heat sinking plate  125 , including the light source unit  129 ,  130 , and the QD bar  140  are arranged at the lateral side of the light guide plate  120  and pressed. Consequently, the heat sinking plate  125 , the light source unit  129 ,  130  and the QD bar  140  are closely adjoined to the lateral side of the light guide plate  120 . In this pressed state, if the heat sinking plate  125  is fastened to the adjacent light guide plate supporting frame  124  or to the middle molding part  126 , the QD bar  140  is fastened without any separate QD-bar fastening unit. No adhesive layer is used between the LED  30  and the QD bar  140 , or between the QD bar  140  and the light guide plate  120 , thus preventing light distortion caused by adhesive layers. 
     In  FIG. 17 , the heat sinking plate  125  is used as a pressing member for pressing the QD bar  140  toward the lateral side of the light guide plate  120 . The pressing member may be the light source supporting member  129 , the light guide plate supporting frame  124  or the middle molding part  126  as well as the heat sinking plate  125 . 
     Although a few exemplary embodiments have been shown and described, it will be appreciated by those skilled in the art that changes may be made in these exemplary embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.