Patent Publication Number: US-2010123848-A1

Title: Led module and liquid crystal display having the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from Korean Patent Application No. 10-2008-114625, filed on Nov. 18, 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 and methods consistent with the present invention relate to a liquid crystal display, and more particularly, to a light emitting diode (LED) module used in a liquid crystal display. 
     2. Description of the Related Art 
     Liquid crystal displays are a kind of display apparatus that has been widely used for its light weight, compact size, and capability of realizing full-color and high resolution. The liquid crystal display displays images using a liquid crystal which is a light receiving element incapable of emitting light by itself. Therefore, a backlight unit is required to supply light to a liquid crystal panel. 
     Lamps are mainly used as a light source for the backlight unit. Recently, for the purpose of achieving compactness of the liquid crystal display, an attempt has been made to apply a light emitting diode (LED) to the backlight unit. Since a single liquid crystal display requires many LEDs, an LED module having a plurality of LEDs is preferred. With the application of the LEDs to the backlight unit, components necessary for the lamp such as an inverter are not required and noise by high voltage can be reduced. 
     The LED emits a large amount of heat if the liquid crystal display is used for a long time. The high temperature reduces a lifespan of the LED and causes the LED to be defective. Therefore, a heat dissipating device is required to dissipate heat generated in the LED. However, due to such an extra heat dissipating device, the number of manufacturing processes increases and a manufacturing cost increases. 
     SUMMARY OF THE INVENTION 
     Exemplary embodiments of the present invention overcome the above 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. 
     The present invention provides an LED module, which simplifies a manufacturing process and effectively cools an LED, and a liquid crystal display having the same. 
     According to an aspect of the present invention, an LED module includes a plurality of LEDs which emit light, and a metal substrate on which the LEDs are mounted and which has a fixing part to be directly fixed to an outer frame, wherein the metal substrate itself absorbs heat generated by the LEDs. 
     The LEDs may be integrally formed with the metal substrate. 
     The metal substrate may include a first metal substrate on which the LEDs are mounted, and a second metal substrate on which the fixing part is formed and which absorbs heat generated by the LEDs. 
     The first and the second metal substrates may be adhered to each other by soldering. 
     The fixing part may be a through hole which is formed on a surface neighboring one surface of the metal substrate on which the LEDs are mounted. 
     The fixing part may be a through hole which is formed on a surface opposite one surface of the metal substrate on which the LEDs are mounted. 
     The metal substrate may have a thickness ranging from two times to ten times larger than a width of the LEDs. 
     According to another aspect of the present invention, a liquid crystal display includes a liquid crystal panel which displays an image, an LED module which supplies light to the liquid crystal panel, and a light guide plate which guides light emitted from the LED module toward the liquid crystal panel. 
     Additional and/or other aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
       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 a liquid crystal display consistent with an exemplary embodiment of the present invention; 
         FIG. 2  is an enlarged view of the LED module of  FIG. 1 ; and 
         FIG. 3  is a view of an LED module consistent with another exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS 
     Certain exemplary embodiments of the present invention will now be described in greater detail with reference to the accompanying drawings. 
     In the following description, 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 a liquid crystal display according to an exemplary embodiment of the present invention. 
     As shown in  FIG. 1 , a liquid crystal display  100  comprises an upper casing  110 , a lower casing  120 , a liquid crystal panel  130 , and a backlight unit  200 . 
     The upper casing  110  and the lower casing  120  together form the exterior of the liquid crystal display  100  and fix interior components of the liquid crystal display  100 . 
     The liquid crystal panel  130  displays an image using light supplied from the backlight unit  200 . Since the operation and function of the liquid crystal panel  130  is readily understood by a person of ordinary skill in the related art, a detailed description thereof will be omitted. 
     The backlight unit  200  supplies light to the liquid crystal panel  130  and includes an LED module  210 , a light guide plate  220 , an optical sheet  230 , and a reflective sheet  240 . 
     The LED module  210  is used as a light source for the backlight unit  200  and is disposed around edges of the liquid crystal panel  130 . 
     The light guide plate  220  guides light emitted from LEDs  211  toward the light crystal panel  130 . The light guide plate  220  is a flat board having a predetermined thickness and may be formed of transparent acryl, polymethylmethacrylate, plastic or glass. 
     The optical sheet  230  is disposed on the light guide plate  220  and diffuses and collects light directed to the liquid crystal panel  130 . The optical sheet  230  may comprises a diffusing plate (not shown) and a prism sheet (not shown). 
     The reflective sheet  240  is disposed under the light guide plate  220  and reflects light directed downward from the light guide plate  220  toward the liquid crystal panel  130 . 
     The light guide plate  220 , the optical sheet  230 , and the reflective sheet  240  can be easily understood by an ordinary skilled person in the related art and thus detailed description thereof will be omitted. 
       FIG. 2  is an enlarged view of the LED module  210  of  FIG. 1 . Referring to  FIG. 2 , the LED module  210  will be described in greater detail. 
     The LED module  210  comprises a plurality of connectors  211 , a plurality of LEDs  212 , and a metal substrate  213 . 
     The connectors  211  are connected to a power supply (not shown) to supply power to the LEDs  212 . The connectors are located at opposite ends of the metal substrate  213 . 
     The LEDs  212  are mounted on a surface of the metal substrate  213  in line. The LEDs  212  are electrically connected to one another through a wire (not shown). If power is supplied to the LEDs  212 , the LEDs  212  emit light toward the light guide plate  220 . 
     If the liquid crystal display  100  is used for a long time, the temperature of the LEDs  212  greatly increases. In order to prevent damage to the LEDs  212 , dissipation of the heat generated by the LEDs  212  is required. According to a related art method of dissipating heat, an extra heat dissipating device is attached to the metal substrate  213 . However, there is a minute air gap between the heat dissipating device and the metal substrate  213 , which increases heat resistance and deteriorates heat dissipating performance of the LEDs  212 . Due to an additional process of attaching the heat dissipating device to the metal substrate  213 , the number of manufacturing processes increases and the manufacturing cost increases. 
     According to an exemplary embodiment of the present invention, the metal substrate  213  itself serves as a heat sink to absorb heat generated by the LEDs  212 . To this end, the metal substrate  213  has a predetermined thickness (t) which is sufficient to serve as a heat sink and is integrally formed with the LEDs  212 . Since the heat generated by the LEDs  212  is directly transmitted to the metal substrate  213 , no air gap is created and accordingly heat dissipating performance of the LEDs  212  is improved. Also, an additional process of attaching an extra heat dissipating device is not required. 
     As the thickness of the metal substrate  213  increases, the cost increases and the size of the liquid crystal display  100  increases. Accordingly, there is necessity to adjust the thickness of the metal substrate  213  properly. The thickness of the metal substrate  213  may be about two times to about ten times larger than the width (w) of the LEDs  212 . 
     The metal substrate  211  comprises a fixing part  214  to fix the LED module  210  to an outer frame directly. According to an exemplary embodiment of the present invention, the lower casing  120  corresponds to the outer frame. Conventionally, an extra component is required to fix the LED module  210  to the lower casing  120 . However, according to an exemplary embodiment of the present invention, since the fixing part  214  is integrally formed with the metal substrate  213 , an extra component for fixing the LED module  210  is not required. Accordingly, the manufacturing process can be simplified. 
     As shown in  FIG. 2 , the fixing part  214  may be a through hole. According to an exemplary embodiment of the present invention, the through hole  214  is provided on a surface A neighboring the surface of the metal substrate  213  on which the LEDs  212  are mounted. However, this should not be considered as limiting since the through hole  214  may be provided on other surfaces of the metal substrate  213 . For example, the through hole  214  may be provided on a surface B opposite the surface of the metal substrate  213  on which the LEDs  212  are mounted. A screw is inserted into the through hole  214  to fix the LED module  210  to the lower casing  120 . 
       FIG. 3  is a view of an LED module according to another exemplary embodiment of the present invention. 
     The same reference numerals are used for the same elements as in the aforementioned embodiment. 
     According to another exemplary embodiment of the present invention, an LED module  210   a  comprises a plurality of connectors  211 , a plurality of LEDs  212 , and a metal substrate  213 . 
     The metal substrate  213  comprises a first metal substrate  213   a  and a second metal substrate  213   b.    
     The LEDs  212  are mounted on the first metal substrate  213   a  which is has a thin plate shape. 
     A fixing part  214  is provided on the second metal substrate  213   b . Since the second metal substrate  213   b  serves as a heat sink to absorb heat generated by the LEDs  212 , the second metal substrate  213   b  has a predetermined thickness which is sufficient to serve as a heat sink. 
     If a lower casing  120   a  has a complicated shape, such as a curved surface rather than a rectangular shape, the metal substrate  213  should have a shape corresponding to the lower casing  120   a . In this case, it is difficult to integrally form the LEDs  212  with the metal substrate  213 . In order to solve this problem, another exemplary embodiment of the present invention uses the first metal substrate  213   a  and the second metal substrate  213   b . Since the first metal substrate  213   a  has a thin plate shape, the LEDs  212  can be easily mounted on the first metal substrate  213   a . The second metal substrate  213   b  has a shape corresponding to the lower casing  120   a.    
     The first and the second metal substrates  213   a ,  213   b  may be adhered to each other by soldering, adhesive or other techniques known in the art. Since the first and the second metal substrates  213   a ,  213   b  are adhered to each other, an air gap is not created between the first and the second metal substrates  213   a ,  213   b , thereby improving the heat dissipating performance of the LEDs  212 . 
     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.