Abstract:
A backlight unit adapted to prevent light leakage and damage of its internal components due to a thermal deformation is disclosed. 
     The backlight unit includes: a bottom cover with an opened upper surface; a printed-circuit-board disposed on at least one inner side surface of the bottom cover; a plurality of LEDs loaded on the printed-circuit-board; and a plurality of slits formed on at least one edge of the bottom cover opposite to the printed-circuit-board and configured to reduce thermal deformation of the bottom cover.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority under 35 U.S.C. 119 to Korean Patent Application No. 10-2009-0072060, filed on Aug. 5, 2009, which is hereby incorporated by reference in its entirety. 
     BACKGROUND 
     1. Field of the Disclosure 
     This disclosure relates to a backlight unit, and more particularly to a backlight unit adapted to prevent light leakage caused by a thermal deformation, and a liquid crystal display (LCD) device with the same. 
     2. Description of the Related Art 
     Cathode ray tubes (CRTs), which correspond to one of widely used display devices, are mainly used as monitors for TVs, measuring apparatuses, or information terminals. However, the heavy weight and large size of the CRTs have been a major hindrance to the manufacturing of small, light electronic products. 
     To address this matter, LCD devices are gradually being used in a wide range of applications due to their advantages such as lightness, thinness, and low power consumption. Accordingly, LCD devices are being manufactured to have even larger screens, be thinner, and consume less power, in order to meet requirements of users. Such LCD devices display images by controlling the amount of light transmitted through liquid crystal. 
     LCD devices are not self-illuminating display devices, unlike CRTs. As such, an LCD device includes a backlight unit provided on the rear surface of an LCD panel. The backlight unit includes a separated light source providing light necessary to display an image. Actually, the backlight unit employs cold cathode fluorescent lamps (CCFLs) with electrodes encompassing both end circumferences of a lamp, external electrode fluorescent lamps (EEFLs) with electrodes inserted into both ends of a lamp, light emitting diodes (LEDs), or others, as a light source. Recently, LEDs are being mainly used as the light source of a backlight unit because they are suitable for the slimness and low power consumption of the backlight unit. 
     A backlight unit of the related art employing the LEDs as a light source is configured to include a box-shaped bottom cover with an opened surface and a metal printed circuit board (PCB) disposed on at least one inner side surface and loaded with a plurality of LEDs. The bottom cover is formed from a metal material. The backlight unit is further configured to include a light guide plate disposed parallel to the plurality of LEDs. The light guide plate converts spotted lights from the plurality of LEDs into a two-dimensional light and applies the two-dimensional light to a LCD panel which is disposed on it. 
     The LEDs are most suitable to make slimness and low power consumption of the backlight unit, as described above. On the other hand, the lifespan of LEDs can be reduced by heat generated during the driving of the LEDs. 
     The metal PCB disposed on the inner side surface of the bottom cover transfers heat generated in the plurality of LEDs to the bottom cover which is formed from a metal material. Therefore, the related art backlight unit can prevent the reduction of the LED lifespan. 
     However, since the related art backlight unit forces the heat generated in the plurality of LEDs to be transferred to the side surface of the bottom cover, the heat is concentrated to the side surface of the bottom cover. As such, the bottom cover is deformed by the heats concentrated to its side surface. This results from the fact that the bottom cover of a metal material easily expands and contracts with heat. 
     More specifically, the concentrated heat forces the side surface of the bottom cover to be thermally deformed to have a bent shape. Due to this, components within the bottom cover can be damaged. Also, the bent side surface of the bottom cover causes light to be leaked from the edge of the bottom cover, so that brightness of the backlight unit (and the LCD device) is deteriorated. Consequently, the thermal deformation of the bottom cover can deteriorate displaying quality of the LCD device. 
     BRIEF SUMMARY 
     Accordingly, the present embodiments are directed to a backlight unit that substantially obviates one or more of problems due to the limitations and disadvantages of the related art, and an LCD device with the same. 
     An object of the present embodiments is to provide a backlight unit that is adapted to prevent light leakage and damage of its internal components due to a thermal deformation. 
     Another object of the present embodiments is to provide an LCD device that is adapted to improve displaying quality. 
     Additional features and advantages of the embodiments 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 embodiments. The advantages of the embodiments will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 
     According to one general aspect of the present embodiment, a backlight unit includes: a bottom cover with an opened upper surface; a printed-circuit-board disposed on at least one inner side surface of the bottom cover; a plurality of LEDs loaded on the printed-circuit-board; and a plurality of slits formed on at least one edge of the bottom cover opposite to the printed-circuit-board and configured to reduce thermal deformation of the bottom cover. 
     An LCD device according to another general aspect of the present embodiment, includes: a liquid crystal display panel; a bottom cover configured to include an opened upper surface and disposed under the liquid crystal display panel; a printed-circuit-board disposed on at least one inner side surface of the bottom cover; a plurality of LEDs loaded on the printed-circuit-board; and a plurality of slits formed on at least one edge of the bottom cover opposite to the printed-circuit-board and configured to reduce thermal deformation of the bottom cover. 
     Other systems, methods, features and advantages will be, or will become, apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the following claims. Nothing in this section should be taken as a limitation on those claims. Further aspects and advantages are discussed below in conjunction with the embodiments. It is to be understood that both the foregoing general description and the following detailed description of the present disclosure are exemplary and explanatory and are intended to provide further explanation of the disclosure as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the embodiments and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the disclosure. In the drawings: 
         FIG. 1  is a disassembled perspective view showing an LCD device according to an embodiment of the present disclosure; 
         FIG. 2  is a cross-sectional view showing the LCD device taken along a line I-I′ in  FIG. 1 ; 
         FIG. 3  is a planar view showing a bottom cover according to an embodiment of the present disclosure; 
         FIG. 4  is a cross-sectional view showing an LCD device according to another embodiment of the present disclosure; 
         FIG. 5  is a planar view showing a bottom cover according to another embodiment of the present disclosure; 
         FIG. 6  is a cross-sectional view showing an LCD device according to still another embodiment of the present disclosure; and 
         FIG. 7  is a planar view showing a bottom cover according to still another embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. These embodiments introduced hereinafter are provided as examples in order to convey their spirits to the ordinary skilled person in the art. Therefore, these embodiments might be embodied in a different shape, so are not limited to these embodiments described here. Also, the size and thickness of the device might be expressed to be exaggerated for the sake of convenience in the drawings. Wherever possible, the same reference numbers will be used throughout this disclosure including the drawings to refer to the same or like parts. 
       FIG. 1  is a disassembled perspective view showing an LCD device according to an embodiment of the present disclosure.  FIG. 2  is a cross-sectional view showing the LCD device taken along a line I-I′ in  FIG. 1 .  FIG. 3  is a planar view showing a bottom cover according to an embodiment of the present disclosure. 
     Referring to  FIGS. 1 to 3 , an LCD device according to an embodiment of the present disclosure includes an LCD panel  110  configured to display images, a backlight unit  120  disposed under the LCD panel  110  and configured to apply light to the LCD panel  110 , and a panel guider  118  configured to support edges of the rear surface of the LCD panel  110 . The panel guider  118  is combined with the backlight unit  120 . 
     Although it is not shown in detail in the drawings, the LCD panel  110  includes a thin film transistor substrate  113  and a color filter substrate  111  disposed opposite each other and combined to uniformly maintain a cell gap between them, as well as a liquid crystal layer (not shown) interposed between the two substrates  111  and  113 . On the thin film transistor substrate  113 , a plurality of gate lines are formed, a plurality of data lines are formed to cross the plurality of gate lines, and a plurality of transistors TFT are formed at the intersections of the plurality of gate lines and the plurality of data lines. The color filter substrate  111  includes color filters which are formed opposite pixels, respectively. 
     The LCD device further includes a gate driving printed-circuit-board (PCB)  103  and a data driving PCB  101  disposed by the sides of the LCD panel  110 . The gate driving PCB  103  sequentially applies a scan signal to the gate lines on the LCD panel  110 . The data driving PCB  101  applies data signals to the data lines on the LCD panel  110 . To this end, the gate and data driving PCBs  103  and  101  are electrically connected to the LCD panel  110  by means of COFs (chip on film)  105 . The COFs  105  can be replaced with tape carrier packages (TCPs). 
     The backlight unit  120  includes a box-shaped bottom cover  180  with an opened upper surface, first to fourth light source modules  150   a  to  150   d  arranged on inner side surfaces of the bottom cover  180 , a light guide plate  140  disposed between the first to fourth light source modules  150   a  to  150   d , optical sheets  130  disposed on the light guide plate  140 , and a reflection sheet  160  disposed under the light guide plate  140 . The light guide plate  140  is configured to convert spotted incident lights from the first through fourth light source modules  150   a  through  150   d  into a two-dimensional light. The optical sheets  130  are configured to diffuse and converge the two-dimensional light entered from the light guide plate  140 . The reflection sheet  160  reflects light progressing downward from the light guide plate  140  toward the optical sheets  130 . The first through fourth light source modules  150   a  through  150   d  are configured to each include a metal PCB  151  and a plurality of LEDs  153  loaded on the metal PCB. 
     The backlight unit  120  further includes first to fourth heat radiation plates  170   a  to  170   d  each disposed between the first to fourth light source modules  150   a  to  150   d  and the inner side surfaces of the bottom cover  180 . The first through fourth heat radiation plates  170   a  through  170   d  are used to rapidly transfer heat generated in the first through fourth light source modules  150   a  through  150   d  toward the bottom cover  180 . 
     The box-shaped bottom cover  180  with the opened upper surface is configured to include a bottom surface and first to fourth side surfaces  183   a  to  183   d . Also, the bottom cover  180  is further configured to include a plurality of slits formed along lines which are separated by a fixed distance from the first to fourth side surfaces  183   a  to  183   d . In other words, the plurality of slits are formed at a fixed interval along edges of the bottom surface of the bottom cover  180 . 
     The plurality of slits  181  include first to fourth slits  181   a  to  181   d  with a bar shape. The first slits  181   a  are formed on an edge of the bottom surface adjacent to the first side surface  183   a . The second slits  181   b  are formed on another edge of the bottom surface adjacent to the second side surface  183   b . The third slits  181   c  are formed on still another edge of the bottom surface adjacent to the third side surface  183   c . The fourth slits  181   d  are formed on further still another edge of the bottom surface adjacent to the fourth side surface  183   d . Each of the first to fourth slits  181   a  to  181   d  is formed to extend perpendicularly to the longitude direction of the respective side surface  183   a  to  183   d.    
     Also, the plurality of slits  181  with the first to fourth slits  181   a  to  181   d  are formed on the edge region of the bottom surface opposite to the first through fourth light source modules  150   a  though  150   d  and the first through fourth heat radiation plates  170   a  through  170   d . As such, heat, which is transferred from the first through fourth light source modules  150   a  through  150   d  via the first through fourth heat radiation plates  170   a  through  170   d  toward the bottom cover  180  (more specifically, the first through fourth side surfaces  183   a  through  183   d ), can be partially bypassed to the exterior of the bottom cover  180  via the plurality of slits  181 . In other words, the plurality of slits  181  eases the local concentration of heat in a region of the bottom cover  180  on which the first through fourth light source modules  150   a  through  150   d  and the first through fourth heat radiation plates  170   a  through  170   d  are arranged. Therefore, thermal deformation of the bottom cover  180  caused by the local concentration of heat can be minimized. 
     Although the LCD device according to an embodiment of the present disclosure is described to have the configuration that the plurality of slits  181  are separated by a fixed distance from the side surfaces  183   a  through  183   d  of the bottom cover  180 , it is not limited to this. For example, the plurality of slits  181  can be formed opposite the lower surfaces of the first through four light source modules  150   a  through  150   d  and first through fourth heat radiation plates  170   a  through  170   d , as well as the side surfaces of the first through fourth heat radiation plates  170   a  through  170   d . In other words, the plurality of slits  181  can be positionally changed in the formation. 
     Also, the LCD device according to an embodiment of the present disclosure is disclosed to include the first through fourth light source modules  150   a  through  150   d  disposed on all the inner side surfaces of the bottom cover  180 . However, the LCD device can be configured to include at least one light source module disposed on at least one inner side surface of the bottom cover  180  according to design specifications. 
     Moreover, the plurality of slits  181  provides extra space making it possible for the bottom cover  180  to expand and contract with heat. Therefore, the thermal deformation of the bottom cover  180  can be prevented. 
     In this manner, the LCD device according to an embodiment of the present disclosure can prevent the thermal deformation of the bottom cover  180  caused by the heat which are generated in the first through fourth light source modules  150   a  through  150   d  and concentrated to the side surfaces  183   a  through  183   d  of the bottom cover  180 . As such, damage of components within the LCD device can be prevented. 
     Furthermore, the LCD device according to an embodiment of the present disclosure can prevent the brightness deterioration derived from the thermal deformation of the bottom cover  180 . Therefore, the LCD device can improve displaying quality. 
       FIG. 4  is a cross-sectional view showing an LCD device according to another embodiment of the present disclosure.  FIG. 5  is a planar view showing a bottom cover according to another embodiment of the present disclosure. 
     The LCD device of another embodiment in  FIGS. 4 and 5  has the same configuration as that according to an embodiment of the present disclosure shown in  FIGS. 1 and 3 , with the exception of a bottom cover  280 . As such, the rest of the LCD device according to another embodiment without the bottom cover  280  will be referred to with the same numbers as those according to that embodiment of  FIGS. 1 to 3 . Moreover, the detailed description for the rest of the LCD device of another embodiment without the bottom cover  280  will be omitted. 
     A bottom cover  280  according to another embodiment of the present disclosure is formed in a box-shape with the opened upper surface. The bottom cover  280  is configured to include a bottom surface and first to fourth side surfaces  283   a  to  283   d . Also, the bottom cover  280  is further configured to include a plurality of slits  281  formed along lines which are separated by a fixed distance from the first to fourth side surfaces  283   a  to  283   d . In other words, the plurality of slits  281  are formed at a fixed interval along edges of the bottom surface of the bottom cover  280 . 
     The plurality of slits  281  is formed on the bottom surface opposite to the first through fourth light source modules  150   a  through  150   d  and the first through fourth heat radiation plate  170   a  through  170   d . Also, the plurality of slits  281  includes first to fourth slits  281   a  to  281   d  with a “T” shape. The first slits  281   a  are formed on an edge of the bottom surface adjacent to the first side surface  283   a . The second slits  281   b  are formed on another edge of the bottom surface adjacent to the second side surface  283   b . The third slits  281   c  are formed on still another edge of the bottom surface adjacent to the third side surface  283   c . The fourth slits  281   d  are formed on further still another edge of the bottom surface adjacent to the fourth side surface  283   d.    
     Each of the first through fourth slits  281   a  through  281   d  is formed to have a first hole pattern  287  parallel to the respective side surface  283   a  through  283   d , and a second hole pattern  285  perpendicular to the first hole pattern  287 . The second hole pattern  285  is formed to extend from an middle portion of the first hole pattern toward an inner side of the bottom surface. Consequently, the plurality of slits  281  is formed all in a “T” shape. 
     The first hole pattern  287  is used to prevent a thermal deformation of the bottom cover  280  in a direction parallel to the respective side surface  283  of the bottom cover  280 . The second hole pattern  285  is used to prevent another thermal deformation of the bottom cover  280  in another direction perpendicular to the respective side surface  283  of the bottom cover  280 . For example, the first hole pattern  287  included in the fourth slit  281   d  prevents a thermal deformation of the bottom cover  280  in a first direction of x-x′, and the second hole pattern  285  included in the fourth slit  281  prevents another thermal deformation of the bottom cover  280  in a second direction of y-y′. 
     Consequently, the plurality of slits  281  provides extra space making it possible for the bottom cover  280  to expand and contract with heat. As such, the thermal deformation of the bottom cover  280  in the first and second directions of x-x′ and y-y′ can be prevented. 
     As described above, the LCD device according to another embodiment of the present disclosure can prevent the thermal deformation of the bottom cover  280  caused by the heat which is generated in the first through fourth light source modules  150   a  through  150   d  and concentrated to the side surfaces  283  of the bottom cover  280 . As such, damage of components within the LCD device can be prevented. 
     Furthermore, the LCD device according to another embodiment of the present disclosure can prevent the brightness deterioration derived from the thermal deformation of the bottom cover  180 . Therefore, the LCD device can improve display quality. 
       FIG. 6  is a cross-sectional view showing an LCD device according to still an embodiment of the present disclosure.  FIG. 7  is a planar view showing a bottom cover according to still another embodiment of the present disclosure. 
     The LCD device of still another embodiment in  FIGS. 6 and 7  has the same configuration as that according to an embodiment of the present disclosure shown in  FIGS. 1 and 3 , with the exception of a bottom cover  380 . As such, the rest of the LCD device according to still another embodiment without the bottom cover  380  will be referred to with the same numbers as those according to that embodiment of  FIGS. 1 to 3 . Moreover, the detailed description for the rest of the LCD device of still another embodiment without the bottom cover  380  will be omitted. 
     A bottom cover  380  according to still another embodiment of the present disclosure is formed in a box-shape with an opened upper surface. The bottom cover  380  is configured to include a bottom surface and first to fourth side surfaces  383   a  to  383   d . Also, the bottom cover  380  is further configured to include a plurality of slits  381  formed along lines which are separated by a fixed distance from the first to fourth side surfaces  383   a  to  383   d . In other words, the plurality of slits  381  are formed at a fixed interval along edges of the bottom surface of the bottom cover  380 . 
     The plurality of slits  381  is formed on the bottom plate opposite to the first through fourth light source modules ( 150   a  through  150   d  in  FIG. 1 ) and the first through fourth heat radiation plate ( 170   a  through  170   d  in  FIG. 1 ). Also, the plurality of slits  381  includes first to fourth slits  381   a  to  381   d  with a shape of “+”. The first slits  381   a  are formed on an edge of the bottom surface adjacent to the first side surface  383   a . The second slits  381   b  are formed on another edge of the bottom surface adjacent to the second side surface  383   b . The third slits  381   c  are formed on still another edge of the bottom surface adjacent to the third side surface  383   c . The fourth slits  381   d  are formed on further still another edge of the bottom surface adjacent to the fourth side surface  383   d.    
     Each of the first through fourth slits  381   a  through  381   d  is formed to have a first hole pattern  387  parallel to a longitude direction of the respective side surface  383 , and a second hole pattern  385  perpendicular to the first hole pattern  387 . The first and second hole patterns  387  and  385  are formed to cross each other, so that their middle portions are overlapped with each other. Consequently, the plurality of slits  381  is formed all in the shape of “+”. 
     The first hole pattern  387  is used to prevent a thermal deformation of the bottom cover  380  in a direction parallel to the respective side surface  383  of the bottom cover  380 . The second hole pattern  385  is used to prevent another thermal deformation of the bottom cover  380  in another direction perpendicular to the respective side surface  383  of the bottom cover  380 . For example, the first hole pattern  387  included in the fourth slit  381   d  prevents a thermal deformation of the bottom cover  380  in a first direction of x-x′, and the second hole pattern  385  included in the fourth slit  381   d  prevents another thermal deformation of the bottom cover  380  in a second direction of y-y′. 
     Consequently, the plurality of slits  381  provides extra space making it possible for the bottom cover  380  to expand and contract with heat. As such, the thermal deformation of the bottom cover  380  in the first and second directions of x-x′ and y-y′ can be prevented. 
     In this way, the LCD device according to still another embodiment of the present disclosure can prevent the thermal deformation of the bottom cover  380  caused by the heat which is generated in the first through fourth light source modules  150   a  through  150   d  and concentrated to the side surfaces of the bottom cover  380 . As such, damage of components within the LCD device can be prevented. 
     Moreover, the LCD device according to still another embodiment of the present disclosure can prevent the brightness deterioration derived from the thermal deformation of the bottom cover  380 . Therefore, the LCD device can improve display quality. 
     Although the present disclosure has been limitedly explained regarding only the embodiments described above, it should be understood by the ordinary skilled person in the art that the present disclosure is not limited to these embodiments, but rather that various changes or modifications thereof are possible without departing from the spirit of the present disclosure. Accordingly, the scope of the present disclosure shall be determined only by the appended claims and their equivalents.