Abstract:
A backlight unit including: a light emitting diode (LED) module including a metal substrate and an LED which is disposed on a first side of the metal substrate; a frame on which the LED module is mounted; a first mounting portion formed lengthwise on the LED module; and a second mounting portion formed on the frame, the second mounting portion remaining within a width of the LED module.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from Korean Patent Application No. 10-2008-0094886, filed Sep. 26, 2008, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     Apparatuses consistent with the present invention relate to a liquid crystal display (LCD), and more particularly, to a backlight unit used in the LCD. 
     2. Description of the Related Art 
     An LCD is a display apparatus which is widely used because of its lightness, miniature size, full-color, and high resolution. An LCD displays video using a liquid crystal, which is a light receiving device that is not capable of emitting light by itself, and thus a backlight unit is required to supply light to a liquid crystal panel. 
     Recently, there have been many attempts to further reduce the thickness of the LCD. To reduce the thickness of the LCD, there is a need to reduce the thickness of a backlight unit, which is a main component of the LCD. 
     A light source of a backlight unit generates considerable heat. If the light source is not cooled properly, the heat from the light source may become excessive. Therefore, there is a need to reduce the thickness of a backlight unit and appropriately cool a light source of the backlight unit. 
     SUMMARY OF THE INVENTION 
     Exemplary embodiments of the present invention overcome the above problems and/or disadvantages and other disadvantages not described above. Also, the present invention is not required to overcome the disadvantages described above, and an exemplary embodiment of the present invention may not overcome any of the problems described above. 
     An aspect of embodiments of the present invention provides a compact backlight unit and an LCD having the backlight unit. 
     According to an aspect of the present invention, there is provided a backlight unit including a light emitting diode (LED) module including an LED and a metal substrate on which the LED is mounted; a frame to which the LED module is mounted; a first mounting portion formed lengthwise on the LED module; and a second mounting portion formed on the frame so as to remain within a width of the LED module. 
     The LED module may be inserted into the frame by engagement between the first mounting portion and the second mounting portion. 
     The backlight unit may further include a fixing unit which fastens the LED module inserted into the frame. 
     The fixing unit may include a fixing groove which is formed in one of the metal substrate and the frame; and a fixing projection which is fitted into the fixing groove. 
     The fixing unit may further include an elastic member which pushes the fixing projection towards the fixing groove after the LED module is completely inserted into the frame. 
     The fixing unit may be fitted into the second mounting portion after the LED module is completely inserted into the frame. 
     The first mounting portion may be formed on the opposite side to a side of the metal substrate on which the LED is formed. 
     The first mounting portion may be formed on one side of the metal substrate. 
     The first mounting portion may be formed on both sides of the metal substrate. 
     The first mounting portion may have the form of a slit, and the second mounting portion may have the form of a rib corresponding to the slit. 
     The first mounting portion may have the form of a rib, and the second mounting portion may have the form of a slit corresponding to the rib. 
     The first mounting portion may have the form of a T-shaped slit. 
     The first mounting portion may have the form of an L-shaped slit. 
     The first mounting portion may have the form of a straight slit. 
     The first mounting portion may have a plurality of slits. 
     The first mounting portion and the second mounting portion may have grooved surfaces formed thereon. 
     The LED module may be disposed on an edge of a liquid crystal panel. 
     The LED module may be disposed below the liquid crystal panel. 
     According to an aspect of the present invention, there is provided an LCD including a liquid crystal panel which displays an image; and a backlight unit, which supplies light to the liquid crystal panel. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and/or other aspects of the present invention will be more apparent by describing certain exemplary embodiments of the present invention with reference to the accompanying drawings, in which: 
         FIG. 1  is an exploded perspective view of an LCD according to an exemplary embodiment of the present invention; 
         FIG. 2  is a sectional view of a backlight unit shown in  FIG. 1 ; 
         FIGS. 3A to 3E  illustrate exemplary configurations of a first mounting portion and a second mounting portion; 
         FIG. 4  is a partial sectional view of a fixing unit, taken along line A-A in  FIG. 1 ; 
         FIG. 5  is an exploded perspective view of an LCD according to another exemplary embodiment of the present invention; and 
         FIG. 6  is a sectional view of the LCD of  FIG. 5  when an LED module is attached to a frame. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Exemplary embodiments of the present invention are described in greater detail below with reference to the accompanying drawings. 
     In the following description, the same drawing reference numerals are used for the same elements even in different drawings. The matters defined in the description, such as detailed construction and elements, are provided to assist in a comprehensive understanding of the invention. Thus, it is apparent that the exemplary embodiments of the present invention can be carried out without those specifically defined matters. Also, well-known functions or constructions are not described in detail since they would obscure the invention with unnecessary detail. 
       FIG. 1  is an exploded perspective view of an LCD  100  according to an exemplary embodiment of the present invention, and  FIG. 2  is a sectional view of a backlight unit  200  shown in  FIG. 1 . 
     The LCD  100  shown in  FIG. 1  includes an upper case  110 , a lower case  120 , a liquid crystal panel  130 , and a backlight unit  200 . 
     The upper case  110  and lower case  120  form the exterior of the LCD  100 , and house internal components of the LCD  100 . 
     The liquid crystal panel  130  receives light from the backlight unit  200  and displays an image. The configuration and functions of the liquid crystal panel  130  are known to those skilled in the art. 
     The backlight unit  200  supplies light to the liquid crystal panel  130 . The backlight unit  200  includes an LED module  210 , a frame  220 , a first mounting portion  230 , a second mounting portion  240 , a fixing unit  250 , a light guide plate (LGP)  260 , an optical sheet  270 , and a reflective sheet  280 . 
     The LED module  210  is used as a light source of the backlight unit  200 . The LED module  210  is disposed on an edge of or proximate to an edge boundary of the liquid crystal panel  130 , so the backlight unit  200  shown in  FIG. 1  is referred to as an edge-type backlight unit. The LED module  210  includes one or more LEDs  211 , a metal substrate  212 , and connectors  213 . 
     The LEDs  211  are arranged in series on the metal substrate  212 , as shown in  FIG. 1 , and are connected to each other electrically by a wire (not shown). When a power source supplies power to the LEDs  211 , the LEDs  211  emit light to the LGP  260 . As technology has developed, the LEDs  211  may be substantially reduced in size to reduce the thickness of the backlight unit  200 . Accordingly, the thickness of the backlight unit  200  may be determined by the total thickness of the LGP  260 , optical sheet  270 , and reflective sheet  280 , but the size of the LED module  210  does not affect the thickness of the backlight unit  200 . In other words, referring to  FIG. 2 , the size of the LED module  210  may be less than the total thickness of the LGP  260 , optical sheet  270  and reflective sheet  280 . 
     The LEDs  211  are arranged on a first side  214  of the metal substrate  212  in series. The wire electrically connecting the LEDs  211  is also disposed on the metal substrate  212 . Additionally, heat generated by the LEDs  211  is transferred to the frame  220  through the metal substrate  212 . 
     The connectors  213  are connected to a power source (not shown), which supplies power to the LEDs  211 . The connectors  213  are disposed on both ends of the metal substrate  212 . 
     The frame  220  is disposed on an edge of the liquid crystal panel  130 , and is secured on the lower case  120 . The LED module  210  is attached to the frame  220 . 
     The first mounting portion  230  is formed lengthwise on the LED module  210  and extends along substantially the entire length of the LED module  210 . 
     The second mounting portion  240  extends from the frame  220  so as to remain within width W of the LED module  210 . As shown in  FIGS. 1 and 2 , the second mounting portion  240  may have a shape corresponding to the first mounting portion  230 , and thus the first mounting portion  230  and second mounting portion  240  may be matchingly engaged to each other so that the LED module  210  may be inserted into the frame  220 . 
     If the LED module  210  is mounted to the frame  220  by screw engagement, instead of using the first mounting portion  230  and second mounting portion  240 , productivity may be reduced because assembly of the screw engagement requires considerable time. Furthermore, as the size of the liquid crystal panel  130  increases, the length of the LED module  210  also increases, and thus much time may be required for the screw engagement. Additionally, the number of screws required for assembly of the screw engagement may also increase, and accordingly manufacturing costs may increase. Furthermore, if an external shock is applied to the LCD  100 , the screws may damage the wire disposed on the metal substrate  212 . However, according to the exemplary embodiment of the present invention, the LED module  210  is inserted and mounted to the frame  220  by the first mounting portion  230  and second mounting portion  240 , and therefore it is possible to prevent problems due to the screw engagement. 
     As described above, the second mounting portion  240  extends from the frame  220  to remain within width W of the LED module  210 . Referring to  FIG. 2 , the height of the frame  220  from the lower case  120  may be equal to or less than the height of the LED module  210  disposed on the frame  220  from the lower case  120 . In the exemplary embodiment, the frame  220  and the LED module  210  disposed on the frame  220  are the same height from the lower case  120 . Since the LED module  210  may be stably fixed to the frame  220  by the first mounting portion  230  and second mounting portion  240 , there is no need to additionally fix an upper portion of the LED module  210 . Accordingly, it is possible to reduce the thickness of the backlight unit  200 . As described above, the thickness of the backlight unit  200  may be determined according to the total thickness of the LGP  260 , optical sheet  270  and reflective sheet  280 , but the size of the LED module  210  does not affect the thickness of the backlight unit  200 . 
     If the LCD  100  is used for a long period of time, the temperature of the LEDs  211  may rise. To prevent the LEDs  211  from being damaged, the temperature of the LEDs  211  needs to be kept below about 80° C. According to the exemplary embodiment of the present invention, the heat generated by the LEDs  211  is transferred to the frame  220  through the metal substrate  212 , and thus the frame  220  may function as a heat sink. As shown in  FIGS. 1 and 2 , the first mounting portion  230  has the form of a slit formed in the metal substrate  212 , and the second mounting portion  240  has the form of a rib corresponding to the slit and extending from the frame  220 . Accordingly, a contact area between the metal substrate  212  and the frame  220  may be increased, compared to a situation in which the LED module  210  is engaged with the frame  220  by the screw engagement. Thus, it is possible to improve the cooling performance of the LEDs  211 . Consequently, in the exemplary embodiment, it is possible to reduce the thickness of the backlight unit  200  and improve the cooling performance of the LEDs  211 . 
     In the exemplary embodiment, the first mounting portion  230  includes two slits formed on a second side  216  of the metal substrate  212 , opposite to the first side  214  of the metal substrate  212  on which the LEDs  211  are arranged. While the first mounting portion  230  has the form of slits and the second mounting portion  240  has the form of ribs in the exemplary embodiment, the first mounting portion  230  and second mounting portion  240  may have various shapes and structures, for example, the first mounting portion  230  may be configured in the form of one or more ribs and the second mounting portion  240  may be configured in the form of one or more slits.  FIGS. 3A to 3E  illustrate various exemplary configurations of the first mounting portion  230  and the second mounting portion  240  which are shown enlarged in order to facilitate understanding of the exemplary embodiments. 
     In  FIG. 3A , a first mounting portion  230 _ 1  has a T-shaped slit disposed about a middle portion  217  of the metal substrate  212 . The second mounting portion  240 _ 1  has a matching T-shaped rib corresponding to the T-shaped slit. 
     In  FIG. 3B , a first mounting portion  230 _ 2  has two straight slits on third and fourth opposing sides  218  and  222  of the metal substrate  212 . The third side  218  and the fourth side  222  neighbor the first side  214 . A second mounting portion  240 _ 2  has matching two ribs corresponding to the two straight slits. In this case, the second mounting portion  240 _ 2  is formed to remain within width W of the LED module  210 , in order to prevent an increase in the thickness of the backlight unit  200 . 
     In  FIG. 3C , a first mounting portion  230 _ 3  has a straight slit extending from the fourth side  222  of the metal substrate  212  toward the third side  218 . A second mounting portion  240 _ 3  has a matching rib corresponding to the straight slit. In this situation, the second mounting portion  240 _ 3  is formed to remain within width W of the LED module  210 , to prevent an increase in the thickness of the backlight unit  200 . 
     In  FIG. 3D , a first mounting portion  230 _ 4  has an L-shaped slit  254 . A first portion  256  of the L-shaped slit  254  may extend from the second side  216  of the metal substrate  212  toward the first side  214  of the metal substrate  212  on which the LEDs  211  are arranged. A second portion  258  of the L-shaped slit  254  may extend in a direction from the fourth side  222  to the third side  218 . A second mounting portion  240 _ 4  has a matching rib corresponding to the L-shaped slit. 
     In  FIG. 3E , a first mounting portion  230 _ 5  has an L-shaped slit, similar to  FIG. 3D  and a second mounting portion  240 _ 5  has a matching rib. In addition, surfaces of the L-shaped slit and the matching rib have grooved surfaces. Accordingly, the contact area between the metal substrate  212  and the frame  220  may be increased, and thus the cooling performance of the LEDs  211  may be improved. Additionally, the LED module  210  may be secured to the frame  220  more stably. 
     The configurations of the first mounting portion and second mounting portion shown in  FIGS. 3A to 3E  are merely exemplary illustrations, and thus the first mounting portion and second mounting portion may vary in shape and structure. 
       FIG. 4  is a partial sectional view of the fixing unit  250 , taken along line A-A in  FIG. 1 . The fixing unit  250  fastens the LED module  210  inserted into the frame  220 , so as to prevent the LED module  210  from being detached from the frame  220 . The fixing unit  250  includes a fixing groove  251 , a fixing projection  252 , and an elastic member  253 . 
     The fixing groove  251  is formed on one end of the metal substrate  212 . The shape of the fixing projection  252  extending from the frame  220  corresponds to the shape of the fixing groove  251 , so that the fixing projection  252  may be inserted into the fixing groove  251 . The fixing projection  252  is connected to the elastic member  253 . When the LED module  210  is being inserted into the frame  220 , the metal substrate  212  pushes the fixing projection  252 . After the LED module  210  is completely inserted into the frame  220 , the fixing projection  252  is made to slide into place in the fixing groove  251  by the elastic member  253  to be fitted into the fixing groove  251 . 
     The fixing unit  250  configured as described above is merely exemplary. Alternatively, the fixing groove  251  may be formed on the frame  220 , and the fixing projection  252  may extend from the metal substrate  212 . Thus, the fixing unit  250  may have various shapes and structures capable of fastening the LED module  210  that has been inserted into the frame  220 . 
     The LGP  260  guides light emitted from the LEDs  211  towards the liquid crystal panel  130 . The LGP  260  is a plate member having a predetermined thickness, and may be made of, for example, transparent acryl, polymethylmethacrylate (PMMA), plastic, or glass. 
     The optical sheet  270  is disposed above the LGP  260  to diffuse and/or concentrate light. The optical sheet  270  may include a light diffusion plate and/or a prism sheet. 
     The reflective sheet  280  is disposed below the LGP  260 , to reflect light emitted from the LEDs  211  towards the liquid crystal panel  130 . 
     Another exemplary embodiment of the present invention is described below with reference to  FIGS. 5 and 6 . 
       FIG. 5  is an exploded perspective view of an LCD  100 ′ according to an exemplary embodiment of the present invention, and  FIG. 6  is a sectional view of the LCD  100 ′ of  FIG. 5  when an LED module  210  is attached to a frame  220 . 
     Components capable of performing the same functions and operations as those of the components described above with reference to  FIGS. 1 ,  2 ,  3 , and  4  are designated by the same reference numbers, so no further description thereof is required. 
     The LCD  100 ′ of  FIG. 5  includes an upper case  110 , a lower case  120 , a liquid crystal panel  130 , and a backlight unit  200 ′. 
     As shown in  FIGS. 5 and 6 , the backlight unit  200 ′ includes an LED module  210 , a frame  220 , a first mounting portion  230 ′, a second mounting portion  240 ′, a fixing unit  250 ′ and an optical sheet  270 . The LED module  210  is disposed below the liquid crystal panel  130  to provide light directly to the entire surface of the liquid crystal panel  130 , which differs from the backlight unit  200  shown in  FIG. 1 . The backlight unit  200 ′ is referred to as a direct-type backlight unit. Since the LED module  210  described above with reference to  FIG. 1  is disposed on the edge of the liquid crystal panel  130 , light is supplied towards a side surface of the liquid crystal panel  130 , so the LGP  260  is required. However, in this exemplary embodiment of the present invention with reference to  FIGS. 5 and 6 , the LGP  260  is not required because the LED module  210  shown in  FIG. 5  supplies light directly to the entire surface of the liquid crystal panel  130 . 
     The first mounting portion  230 ′ is engaged with the second mounting portion  240 ′ so that the LED module  210  is inserted into the frame  220  in the same manner as described above with reference to  FIG. 1 . Referring to  FIG. 6 , only the LEDs  211  are disposed above the frame  220 , and the metal substrate  212  is disposed inside the frame  220 . Accordingly, the thickness of the backlight unit  200 ′ may be reduced. Additionally, as the first mounting portion  230 ′ and the second mounting portion  240 ′ are configured in the form of a slit or rib, the contact area between the metal substrate  212  and the frame  220  increases, improving the cooling performance of the LEDs  211 . Furthermore, there is no need to use screws to engage the LED module  210  with the frame  220 , to increase productivity. 
     In the same manner as described above with reference to  FIG. 1 , the first mounting portion  230 ′ and the second mounting portion  240 ′ may vary in shape and position. Additionally, the first mounting portion  230 ′ and the second mounting portion  240 ′ may have grooved surfaces to improve the cooling performance of the LEDs  211 , caused by an increase in the contact area between the metal substrate  212  and the frame  220 . 
     After the LED module  210  is completely inserted into the frame  220 , the fixing unit  250 ′ is fitted into the second mounting portion  240 ′ formed in the frame  220 , to prevent the LED module  210  from being separated from the frame  220 . 
     The fixing unit  250 ′ may be made of elastic material which has a thickness slightly greater than that of the second mounting portion  240 ′. Accordingly, if the fixing unit  250 ′ is fitted into the second mounting portion  240 ′, the LED module  210  may be fastened to the frame  220 . 
     The foregoing exemplary embodiments and advantages are merely exemplary and are not to be construed as limiting the present invention. The present teaching can be readily applied to other types of apparatuses. Also, the description of the exemplary embodiments of the present invention is intended to be illustrative, and not to limit the scope of the claims, and many alternatives, modifications, and variations will be apparent to those skilled in the art.