Patent Publication Number: US-10324252-B2

Title: Backlight unit

Description:
This is a divisional application of copending application Ser. No. 14/743,719, filed on Jun. 18, 2015, which is a divisional application of application Ser. No. 13/726,733, filed on Dec. 26, 2012 (now U.S. Pat. No. 9,099,018), which claims the priority benefit of Korean Patent Application No. 10-2012-0089627 filed in the Republic of Korea on Aug. 16, 2012, all of which are hereby incorporated by reference in their entirety. 
    
    
     BACKGROUND 
     Field of the Disclosure 
     The present disclosure relates to a backlight unit that is used in a display device. 
     Discussion of the Related Art 
     A general liquid crystal display device  10  includes a liquid crystal panel  20  for outputting images, and a cover bottom  30  for receiving the liquid crystal panel  20  therein, as shown in  FIG. 1 . 
     On a rear surface of the cover bottom  30 , a reinforcement frame  31  coupled to upper and lower portions, a reinforcing bar  22  for supporting the reinforcement frame  31 , and a screw type of fixing member  33  for fixing and coupling the reinforcing bar  22  and the cover bottom  30  are positioned. 
     More specifically, the cover bottom  30  is manufactured in the form of a single sheet metal so as to correspond to a size (inch) of the liquid crystal panel  20 , and the cover bottom  30  is laterally distorted due to thermal deformation occurring with respect to the reinforcing bar  22  by heat generated in a light source, thereby adversely affecting the mechanical life of the liquid crystal display device  10 . 
     In addition, it is difficult to manufacture and mold the cover bottom in the form of a single sheet metal corresponding to a size of a liquid crystal panel which has been rapidly increasing. 
     In addition, along with the increase in the size of the cover bottom, a plurality of reinforcing bars should be provided on a rear surface of the cover bottom, resulting in an increase in manufacturing costs. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to a backlight unit for a display device that substantially obviates one or more of the problems due to limitations and disadvantages of the related art. 
     An object of the present disclosure is to provide a backlight unit for a display device which may prevent thermal expansion and thermal deformation of the backlight unit affected by heat generated from a light source of a large display device, and include a cover bottom divided into a plurality of parts and joined to one so as to withstand external shocks. 
     Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 
     To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, a backlight unit includes: a light source; and a cover bottom internally accommodating the light source, wherein the cover bottom is divided into n-numbered (n&gt;1) sub-cover bottoms, and a coupling unit for mutually fixing and coupling the divided sub-cover bottoms is formed at ends of each of the cover bottoms facing each other. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. In the drawings: 
         FIG. 1  is a perspective view showing a liquid crystal display device of the related art; 
         FIG. 2  is an exploded perspective view showing a display device according to an embodiment of the present invention; 
         FIG. 3  is a sectional view showing a coupled cover bottom constituting a backlight unit according to a first embodiment of the present invention; 
         FIG. 4  is a sectional view showing a state in which an alignment member and a coupling member are coupled to a cover bottom shown in  FIG. 3 ; 
         FIG. 5  is a sectional view showing a coupled cover bottom constituting a backlight unit according to a second embodiment of the present invention; 
         FIG. 6  is a sectional view showing a coupled cover bottom constituting a backlight unit according to a third embodiment of the present invention; 
         FIGS. 7A to 7C  are perspective views showing a coupling process of the cover bottom shown in  FIG. 6 ; 
         FIG. 8  is a perspective view showing a coupled cover bottom constituting a backlight unit according to a fourth embodiment of the present invention; 
         FIG. 9A  is a perspective view showing a coupled cover bottom constituting a backlight unit according to a fifth embodiment of the present invention; 
         FIG. 9B  is a sectional view showing a coupling process of a cover bottom constituting a backlight unit according to a fifth embodiment of the present invention; 
         FIG. 10  is a perspective view showing a coupled cover bottom constituting a backlight unit according to a sixth embodiment of the present invention; 
         FIG. 11  is a perspective view showing a coupled cover bottom constituting a backlight unit according to a seventh embodiment of the present invention; and 
         FIG. 12  is a perspective view showing a reinforcing member constituting a backlight unit according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Example embodiments of the present invention are described below in sufficient detail to enable those of ordinary skill in the art to embody and practice the present invention. It is important to understand that the present invention may be embodied in many alternate forms and should not be construed as limited to the example embodiments set forth herein. It will be understood that, although the terms first, second, A, B, etc. may be used herein in reference to elements of the invention, such elements should not be construed as limited by these terms. 
     Hereinafter, preferred embodiments of the present invention will be described in more detail in reference with the accompanying drawings. Throughout the accompanying drawings, the same reference numerals are used to designate the same or similar components, and redundant descriptions thereof are omitted for easier overall understanding. 
       FIG. 2  is an exploded perspective view showing a display device  100  according to an embodiment of the present invention. As shown in  FIG. 2 , the display device  100  includes a panel  110 , a backlight unit, a guide panel  153 , and a top case  154 . Here, the backlight unit is composed of a light source  120 , a light guide plate  130 , a cover bottom  140 , a reflecting sheet  151 , and an optical sheet  152 . 
     More specifically, the panel  110  may be composed of a liquid crystal panel in which a liquid crystal layer is formed between a color substrate and an array substrate so as to output images. 
     In addition, the light source  120  is positioned below the panel  110  so as to emit light to the panel  110 , and is composed of an LED assembly in which a plurality of LEDs  122  are mounted on a printed circuit board  121 . 
     The light guide plate  130  makes the light emitted from the LED  122  incident to the panel  110 , and is preferably provided so as to face an emission direction of the LED  122 . 
     In addition, the cover bottom  140  constituting the backlight unit is positioned below the light guide plate  130 , and internally accommodates the panel  110  and the light source  120 . 
     More specifically, the cover bottom  140  according to an embodiment of the present invention is divided into n-numbered (n&gt; 1 , n being a natural number) cover bottoms. 
     In addition, in an A region of the cover bottom  140  shown in  FIG. 2 , a coupling unit for fixing and coupling ends of the cover bottoms facing each other is formed, and the coupling unit A will be described in further detail described below. 
     Both ends of the cover bottom coupled to the outermost angle of the cover bottom  140  are bent orthogonally to the direction of the panel  110 , and therefore the cover bottom internally accommodates the light guide plate  130 , the reflecting sheet  151 , and the optical sheet  152 . 
     The reflecting sheet  151  according to an embodiment of the present invention shown in  FIG. 2  is positioned between the light guide plate  130  and the cover bottom  140 , and re-reflects light leaked to the outside of the light guide plate  130 , which cannot be propagated into the light guide plate  130 , to a front surface of the panel  110 . 
     The optical sheet  152  is positioned between the panel  110  and the light guide plate  130 , and is composed of a prism sheet for condensing the light passing through the light guide plate  130  and a diffusion sheet for diffusing light. 
     In addition, the guide panel  153  guides the panel  110 , and fixes the optical sheet  152 . 
     The top case  154  covers edges of an upper surface of the panel  110 , and is coupled to the cover bottom along a side border of the guide panel  153  and the cover bottom  140 , and therefore the panel  110  and the backlight unit are integrated. 
       FIG. 3  is a sectional view showing a coupled cover bottom constituting a backlight unit according to a first embodiment of the present invention. 
     An example in which the cover bottom is divided into two will be described. As shown in  FIG. 3 , the cover bottom  140   a  is divided into a plurality of cover bottoms  141   a  and  142   a , and a coupling unit A for fixing and coupling ends of the cover bottoms  141   a  and  142   a  is provided. 
     More specifically, according to the first embodiment, each of the first cover bottom  141   a  and the second cover bottom  142   a  positioned adjacent to the first cover bottom  141   a  includes a bent region in which ends of the first and second cover bottoms  141   a  and  142   a  are bent by 180 degrees so as to form a hemming structure by a hemming process. 
     Next, the second cover bottom  142   a  is laminated on the first cover bottom  141   a.    
     In this manner, a total of four sheet metals of the cover bottom  140   a  constituting the coupling unit A may be laminated, and the number of laminated sheet metals may be variously changed depending on the number of times of the hemming process performed on the end of the cover bottom. 
     In addition, since the coupling unit A is formed in such a manner that multiple sheet metals of the divided cover bottoms are laminated, a thickness of the coupling unit A may be variously changed depending on the size of the panel, and therefore hardness of the cover bottom  140   a  constituting the backlight unit according to the present invention is improved compared to the cover bottom of the related art to which a reinforcing bar is coupled. 
     Accordingly, the coupling unit A may replace a plurality of reinforcing bars provided so as to maintain hardness of the cover bottom according to the related art, thereby reducing manufacturing costs. 
     When high heat generated from a plurality of LEDs  122  constituting the light source  120  is transmitted to the cover bottom  140   a , the divided cover bottoms  141   a  and  142   a  may individually enable thermal expansion and thermal contraction. 
     Therefore, an amount of deformation is offset due to thermal deformation in the bent region constituting the coupling unit A, and therefore there is an effect of preventing distortion of the cover bottom  140   a  occurring due to heat. 
       FIG. 4  is a sectional view showing a state in which an alignment member and a coupling member are coupled to a cover bottom shown in  FIG. 3 . As shown in  FIG. 4 , the coupling unit A further includes a plurality of alignment members  161  and a fastening member  162 . 
     More specifically, the alignment member  161  acts as a PEM nut, and thereby passes through a laminated region of the first cover bottom  141   a  and the second cover bottom  142   a  so as to guide lamination of the divided cover bottoms  140   a , and align the divided cover bottoms  140   a . 
     In addition, the alignment member  161  may fix and couple the laminated cover bottoms  140   a  with each other in addition to guide the lamination of the first and second cover bottoms  141   a  and  142   a , and align the first and second cover bottoms  141   a  and  142   a.    
     The fastening member  162  may fix and couple the divided cover bottoms  140   a  with each other. 
     More specifically, as shown in  FIG. 3 , the screw type of fastening member  162  according to an embodiment of the present invention includes a thread formed on an outer circumferential surface thereof, and passes through the first cover bottom  141   a  and the second cover bottom  142   a  to fix and couple the first and second cover bottoms  141   a  and  142   a.    
     In addition, the fastening member  162  may select and change a variety of means for fixing the cover bottom  140   a  which has been divided into the plurality of cover bottoms to be laminated. 
       FIG. 5  is a sectional view showing a coupled cover bottom constituting a backlight unit according to a second embodiment of the present invention. In the following description of the second embodiment, the same components as or corresponding to those in the above-described first embodiment will be omitted. Hereinafter, with reference to  FIG. 5 , the cover bottom according to the second embodiment will be described. 
     A cover bottom  140   b  according to the second embodiment of the present invention is divided into a plurality of cover bottoms  141   b  and  142   b , and ends of the divided cover bottoms  141   b  and  142   b  are fixed and coupled with each other to thereby constitute a coupling unit A. 
     More specifically, according to the second embodiment shown in  FIG. 5 , each of the first cover bottom  141   b  and the second cover bottom  142   b  positioned adjacent to the first cover bottom  141   b  includes a bent region in which ends of the first and second cover bottoms  141   b  and  142   b  are bent by 180 degrees so as to form a hemming structure by a hemming process. 
     Next, the second cover bottom  142   b  is laminated on the first cover bottom  141   b  to form the coupling unit A so that an end of the second cover bottom  142   b  faces an end of the first cover bottom  141   b.    
     Accordingly, a total of three sheet metals of the cover bottom  140   b  constituting the coupling unit A may be laminated, and the number of laminated sheet metals may be variously changed depending on the number of times of the hemming process performed on the end of the cover bottom. 
     In addition, since the coupling unit A is formed in such a manner that multiple sheet metals of the divided cover bottoms are laminated, a thickness of the coupling unit A may be variously changed depending on the size of a panel, and therefore hardness of the cover bottom  140   b  constituting the backlight unit according to the present invention is improved compared to the cover bottom of the related art to which a reinforcing bar is coupled. 
     Accordingly, the coupling unit A may replace a plurality of reinforcing bars provided so as to maintain hardness of the cover bottom according to the related art, thereby reducing manufacturing costs. 
     When high heat generated from a plurality of LEDs  122  constituting the light source  120  is transmitted to the cover bottom  140   b , the divided cover bottoms  141   b  and  142   b  may individually enable thermal expansion and thermal contraction. 
     Therefore, an amount of deformation is offset due to thermal deformation in the bent region constituting the coupling unit A, and therefore there is an effect of preventing distortion of the cover bottom  140   b  occurring due to heat. 
     In addition, although not shown, in the same manner as in the first embodiment shown in  FIG. 4 , a plurality of alignment members and fastening members may be coupled to the coupling unit A of the cover bottom  140   b  according to the second embodiment. 
       FIG. 6  is a sectional view showing a coupled cover bottom constituting a backlight unit according to a third embodiment of the present invention, and  FIGS. 7A to 7C  are perspective views showing a coupling process of the cover bottom shown in  FIG. 6 . 
     In the following description of the third embodiment, the same components as or corresponding to those in the above-described first and second embodiments will be omitted. Hereinafter, with reference to  FIGS. 6 and 7A to 7C , the cover bottom according to the third embodiment will be described. 
     As shown in  FIG. 6 , a cover bottom  140   c  according to the third embodiment of the present invention is divided into a plurality of cover bottoms  141   c  and  142   c , and ends of the divided cover bottoms  141   c  and  142   c  are fixed and coupled with each other to thereby constitute a coupling unit A. 
     More specifically, according to the third embodiment shown in  FIG. 6 , the first cover bottom  141   c  includes a bent region in which an end of the first cover bottom  141   c  is bent by 180 degrees so as to form a hemming structure by a hemming process, and a predetermined space may be formed in the bent region. 
     In addition, the second cover bottom  142   c  positioned adjacent to the first cover bottom  141   c  includes a bent region in which an end of the second cover bottom  142   c  is bent by 180 degrees so as to form a hemming structure by a hemming process, and a predetermined space may be formed in the bent region. 
     In order to insert the second cover bottom  142   c  into the space formed in the bent region of the first cover bottom  141   c , as shown in  FIG. 7A , the second cover bottom  142   c  is positioned on the first cover bottom  141   c.    
     Next, as shown in  FIG. 7B , the second cover bottom  142   c  is moved in a direction of an arrow, so that the predetermined space formed in the bent region of the first cover bottom  141   c  and the predetermined space formed in the bent region of the second cover bottom  142   c  face each other. 
     Next, as shown in  FIG. 7C , the second cover bottom  142   c  is moved in a direction of an arrow, so that the second cover bottom  142   c  is slidably coupled to the predetermined space formed in the bent region of the first cover bottom  141   c.    
     In addition, as shown in  FIG. 7C , by pressuring, in a press process, a laminated region from below and above in a state in which sheet metals of the first cover bottom  141   c  and the second cover bottom  142   c  are alternately laminated, the coupling unit A for fixing and coupling the first cover bottom  141   c  and the second cover bottom  142   c  may be formed. 
     Therefore, a total of three sheet metals of the cover bottom  140   c  constituting the coupling unit A may be laminated, and the number of laminated sheet metals may be variously changed depending on the number of times of the hemming process performed on the end of the cover bottom. 
     According to the present embodiment, since the first cover bottom  141   c  and the second cover bottom  142   c  are hooked and coupled with each other, hardness of the cover bottom  140   c  constituting the backlight unit according to the present invention is improved compared to the cover bottom of the related art to which a reinforcing bar is coupled. 
     In addition, the coupling unit A may replace a plurality of reinforcing bars provided so as to maintain hardness of the cover bottom of the related art, thereby reducing manufacturing costs. 
     When high heat generated from a plurality of LEDs  122  constituting the light source  120  is transmitted to the cover bottom  140   c , the divided cover bottoms  141   c  and  142   c  may individually enable thermal expansion and thermal contraction. 
     Therefore, an amount of deformation is offset due to thermal deformation in the bent region constituting the coupling unit A, and therefore there is an effect of preventing distortion of the cover bottom  140   c  occurring due to heat. 
     In addition, although not shown, in the same manner as in the first embodiment shown in  FIG. 4 , a plurality of alignment members and fastening members may be coupled to the coupling unit A of the cover bottom  140   c  according to the third embodiment. 
       FIG. 8  is a perspective view showing a coupled cover bottom constituting a backlight unit according to a fourth embodiment of the present invention. In the following description of the fourth embodiment, the same components as or corresponding to those in the above-described embodiments will be omitted. Hereinafter, with reference to  FIG. 8 , the cover bottom according to the fourth embodiment will be described. 
     As shown in  FIG. 8 , the second cover bottom  142   c  may include a forming shape  145   c  in a region excluding a region where the second cover bottom  142   c  and the first cover bottom  141   c  are coupled with each other, using a forming method. 
     More specifically, in a structure of the cover bottom  140   c , the forming shape  145   c  including a predetermined space  147   c  is formed on the uppermost sheet metal of a coupling unit A formed such that sheet metals of the first and second cover bottoms  141   c  and  142   c  are alternately laminated, and therefore hardness of the cover bottom  140   c  may be improved. 
     In addition, although not shown, in the same manner as in the first embodiment shown in  FIG. 4 , a plurality of alignment members and fastening members may be coupled to a laminated region of the cover bottom  140   c  according to the fourth embodiment. 
       FIG. 9A  is a perspective view showing a coupled cover bottom constituting a backlight unit according to a fifth embodiment of the present invention, and  FIG. 9B  is a sectional view showing a coupling process of a cover bottom constituting a backlight unit according to a fifth embodiment of the present invention. In the following description of the fifth embodiment, the same components as or corresponding to those in the above-described embodiments will be omitted. Hereinafter, with reference to  FIGS. 9A and 9B , the cover bottom according to the second embodiment will be described. 
     As shown in  FIG. 9B , the first cover bottom  141   e  and the second cover bottom  142   e  are laminated in a predetermined region. 
     Next, the laminated region is positioned on a press die D including a tox (T) shape. 
     Next, a pressing process is performed using a press machine (M), and then a coupling unit A is formed on the laminated region of the cover bottom  140   c , and therefore the first cover bottom  141   e  and the second cover bottom  142   e  are fixed and coupled with each other. 
     Accordingly, according the fifth embodiment of the present invention, the same alignment member and fastening member as in the first embodiment may not be provided in the coupling unit A of the cover bottom  140   e.    
     Therefore, the coupling unit A according to the present embodiment may replace a plurality of reinforcing bars provided to maintain hardness of the cover bottom according to the related art, thereby reducing manufacturing costs. 
       FIG. 10  is a perspective view showing a coupled cover bottom constituting a backlight unit according to a sixth embodiment of the present invention. In the following description of the sixth embodiment, the same components as or corresponding to those in the above-described embodiments will be omitted. Hereinafter, with reference to  FIG. 10 , the cover bottom according to the sixth embodiment will be described. 
     As shown in  FIG. 10 , it is preferable that a coupling unit A of a cover bottom  140   f  formed such that the cover bottom  140   f  is divided into a plurality of cover bottoms, and the divided cover bottoms are integrally coupled with each other be formed in a direction opposite to the liquid crystal panel  110 . 
     More specifically, the coupling unit A includes a fixing member  149   f  that is slidably coupled with a plurality of bent portions B along an outer circumferential surface of the bent region B. 
     As shown in  FIG. 10 , the bent portion B formed at an end of a first cover bottom  141   f  includes a vertical portion  143   f  that is bent in the direction opposite to the liquid crystal panel, and an extended portion  145   f  that is extended from the vertical portion  143   f  and is horizontal with the first cover bottom  141   f.    
     The bent portion B formed at an end of a second cover bottom  142   f  also includes a vertical portion  144   f  and an extended portion  146   f  so as to correspond to the bent portion B of the first cover bottom  141   f.    
     In addition, as shown in  FIG. 10 , it is preferable that a bent angle between the bent portions B be perpendicular. 
     In addition, as shown in  FIG. 10 , the fixing member  149   f  is slidably coupled along an outer circumferential surface of the bent portion B, and therefore the first cover bottom  141   f  and the second cover bottom  142   f  are integrally fixed and coupled to each other. 
     Therefore, a coupling unit A according to the present embodiment may replace a plurality of reinforcing bars so as to maintain hardness of the cover bottom according to the related art, thereby reducing manufacturing costs. 
     When high heat generated from a plurality of LEDs  122  constituting the light source  120  is transmitted to the cover bottom  140   f , the divided cover bottoms  141   f  and  142   f  may individually enable thermal expansion and thermal contraction. 
     Therefore, an amount of deformation is offset due to thermal deformation in the bent portion B constituting the coupling unit A, and therefore there is an effect of preventing distortion of the cover bottom  140   f  occurring due to heat. 
     In addition, according to the sixth embodiment of the present invention, since the fixing member  149   f  fixes and couples the first and second cover bottoms  141   f  and  142   f , the cover bottom  140   f  may not additionally include an alignment member or a fastening member. 
       FIG. 11  is a perspective view showing a coupled cover bottom constituting a backlight unit according to a seventh embodiment of the present invention. In the following description of the seventh embodiment, the same components as or corresponding to those in the above-described embodiments will be omitted. Hereinafter, with reference to  FIG. 11 , the cover bottom according to the second embodiment will be described. 
     As shown in  FIG. 11 , compared to the coupling unit A of the cover bottom  140   f  according to the sixth embodiment, a bent that is bent in a direction of a cover bottom  140   g  may be further included. 
     More specifically, the coupling unit A includes a fixing member  149   g  that is slidably coupled to a plurality of bent portions B along an outer circumferential surface of the bent portion B. 
     As shown in  FIG. 11 , the bent portion B that is formed at an end of the first cover bottom  141   g  includes a vertical portion  143   g , an extended portion  145   g , and a bent  147   g.    
     The vertical portion  143   g  is bent from an end of the first cover bottom  141   g  in a direction opposite to the liquid crystal panel  110 . 
     In addition, the extended portion  145   g  is extended from the vertical portion  143   g  so as to be horizontal with the first cover bottom  141   g.    
     The bent  147   g  is bent from an end of the extended portion  145   g  in a direction of the first cover bottom  141   g.    
     Accordingly, a bent portion B formed at an end of the second cover bottom  142   g  also includes a vertical portion  144   g , an extended portion  146   g , and a bent  148   g  so as to correspond to the bent portion B of the first cover bottom  141   g.    
     As shown in  FIG. 11 , a bent angle formed between the bent portions B may be variously formed. 
     More specifically, each angle between the vertical portions  143   g  and  144   g  and the extended portions  145   g  and  146   g  may be 90 degrees, and each angle between the extended portions  145   g  and  146   g  and the bents  147   g  and  148   g  may be 45 degrees or less. 
     In addition, as shown in  FIG. 11 , the fixing member  149   g  is slidably coupled along an outer circumferential surface of the bent portion B, and therefore the first cover bottom  141   g  and the second cover bottom  142   g  may be integrally fixed and coupled with each other. 
     Therefore, the coupling unit A according to the present embodiment may replace a plurality of reinforcing bars provided so as to maintain hardness of the cover bottom according to the related art, thereby reducing manufacturing costs. 
     When high heat generated from a plurality of LEDs  122  constituting the light source  120  is transmitted to the cover bottom  140   g , the divided cover bottoms  141   g  and  142   g  may individually enable thermal expansion and thermal contraction. 
     Therefore, an amount of deformation is offset due to thermal deformation in the bent region B constituting the coupling unit A, and therefore there is an effect of preventing distortion of the cover bottom  140   g  occurring due to heat. 
     In addition, according to the seventh embodiment of the present embodiment, since the fixing member  149   g  fixes and couples the first and second cover bottoms  141   g  and  142   g , the cover bottom  140   g  may not additionally include an alignment member or a fastening member. 
       FIG. 12  is a perspective view showing a reinforcing member  170  constituting a backlight unit according to an embodiment of the present invention. 
     As shown in  FIG. 12 , the reinforcing member  170  includes a first reinforcing portion  171 , a second reinforcing portion  173 , and a connection member  177 , which may be commonly applied to the cover bottom according to the first to seventh embodiments of the present invention. 
     More specifically, as shown in  FIG. 12 , the first reinforcing portion  171  includes a coupling groove  172  formed on an inner surface thereof facing the cover bottom, and an opening  175  formed at ends of both sides thereof. 
     Accordingly, the first reinforcing portion  171  is coupled to the cover bottom along a length direction of the cover bottom to thereby support the length direction of the cover bottom. 
     In addition, in the same manner as in the first embodiment, the second reinforcing portion  173  includes a coupling groove  172  formed on an inner surface thereof facing the cover bottom, and an opening  175  formed at ends of the both sides thereof. 
     Accordingly, the second reinforcing portion  173  is coupled to the cover bottom along a width direction of the cover bottom to thereby support the width direction of the cover bottom. 
     A side surface of the cover bottom  140  of  FIG. 2  is inserted into the coupling groove  172  of the first and second reinforcing portions  171  and  173 . 
     The connection member  177  connects an end of the first reinforcing portion  171  and an end of the second reinforcing portion  173 . Here, one end of the connection member  177  is inserted and fixed in the opening  175  of the first reinforcing portion  171 , and the other end thereof is inserted and fixed in the opening  175  of the second reinforcing portion  173 . 
     That is, the reinforcing member  170  according to the embodiments of the present invention is coupled to the cover bottom along a side border of the cover bottom  140  of  FIG. 2  which has been divided into a plurality of cover bottoms and integrally coupled, thereby forming a vertical partition on an inclined surface of the cover bottom  140  of  FIG. 2 . 
     Therefore, the reinforcing member  170  is coupled to the cover bottom so as to cover the entire side border of the cover bottom  140 , thereby preventing damage and deformation of the cover bottom  140  occurring due to external shocks. 
     In addition, when high heat generated from the light source  120  is transmitted to the cover bottom  140  so that expansion and contraction repeatedly occur over the entire surface of the cover bottom  140 , the reinforcing member  170  supports the cover bottom  140  in the length direction and width direction of the cover bottom  140 , thereby preventing distortion of the cover bottom  140  due to heat. 
     As described above, according to the embodiments of the present invention, the cover bottom constituting the backlight unit is formed in a division structure in which the cover bottom is divided into a plurality of cover bottoms, thereby preventing thermal expansion of the cover bottom due to heat generated from the light source, and thermal deformation due to the thermal expansion. 
     In addition, the cover bottom is formed in a division structure, and therefore hardness of the cover bottom is improved compared to the cover bottom of the related art including a reinforcing bar, thereby stably supporting a panel constituting a large display device, and protecting the display device from external shocks. 
     In addition, the coupling unit replaces a reinforcing bar provided on a bottom surface of a cover bottom of a liquid crystal display device according to the related art, thereby reducing manufacturing costs, and improving production yield. 
     In addition, compared to the cover bottom of the related art which is formed as a single sheet metal, the cover bottom according to the present invention has a division structure, and therefore extension is facilitated in response to the size of a panel which has been increasingly larger. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in a backlight unit of the present disclosure without departing from the sprit or scope of the invention. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.