Abstract:
A liquid crystal display (LCD) device having a heat releasing structure is disclosed to effectively release heat generated from heating elements such as an inverter IC and a transformer formed on an inverter PCB (Printed, Circuit Board). The LCD device includes a lower cover; a backlight unit formed on the lower cover and providing light; a liquid crystal panel separated from the backlight unit and provided with light; an inverter PCB that drives the backlight unit; an inverter IC and a transformer mounted on the PCB and generating voltage supplied to the backlight unit; a heat conduction unit attached on the inverter IC and the transformer and heat-conducted; and a shield cover protecting the PCB from the exterior and contacting with the heat conduction unit on the inverter IC and the transformer to release heat.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a liquid crystal display (LCD) device and, more particularly, to an LCD having a heat releasing structure for effectively releasing heat generated from heating elements such as an inverter IC (Integrated Circuit) and a transformer configured on a PCB (Printed Circuit Board). 
         [0003]    2. Description of the Related Art 
         [0004]    In general, an LCD is a device in which an optical anisotropy is changed by applying an electric field to liquid crystal assuming fluidity of liquid and crystalline optical properties. Compared with the conventional cathode ray tubes (CRTs), the LCD has low power consumption, a small volume, can be increased in size, and has high image resolution (minuteness or fineness). 
         [0005]    However, the LCD is a light receiving device that displays images by adjusting the quantity of light received from the exterior, so it needs a light source, namely, a backlight unit, for emitting light to a liquid crystal panel. The backlight unit is divided into an edge type backlight unit and a direct type backlight unit depending on an installation position of a lamp. 
         [0006]    Here, the edge type backlight unit includes a lamp installed at the side of a light guide plate that guides light. A lamp unit includes a lamp that emits light, a lamp holder inserted at both ends of the lamp to protect the lamp, and a lamp housing that covers an outer surface of the lamp and fixes the side of the light guide plate at one side surface thereof in order to reflect light emitted from the lamp toward the light guide plate. 
         [0007]    The edge type backlight unit is commonly employed for relatively small LCD devices such as monitors of notebook computers and desktop computers, and has good light uniformity and long durability and is advantageous for making the LCD devices thinner. 
         [0008]    The direct type backlight unit has been concentratively developed as the size of the LCDs has been increased. A plurality of lamps are arranged in a row on a lower surface of a diffusion plate and directly emit light to a front surface of a liquid crystal panel. The direct type backlight unit has a high light usage efficiency compared with the edge type backlight unit, so it is mainly used for a large-screen LCD that requires a high luminance. 
         [0009]    The direct type backlight unit is divided into a light emitting part and a wave guiding part. The wave guiding part is an optical component system that changes light emitted from a light emitting lamp to a uniform surface light source, including a reflective plate, a diffusion plate and a prism sheet. The light emitting part includes the light emitting lamp, an inverter that supplies power to light emitting lamp, and a shield cover that protects the inverter. 
         [0010]      FIG. 1  is an exploded perspective view of a general direct type LCD. 
         [0011]    As shown in  FIG. 1 , the LCD includes a direct type backlight unit  20  that provides light to a liquid crystal panel  10  that displays a screen image. 
         [0012]    The liquid crystal panel  10  includes a TFT substrate, a color filter substrate, and liquid crystal injected between the two substrates. Also, the liquid crystal panel  10  includes a data PCB, a gate PCB, a TCP (Tape Carrier Package) of a data side, and a TCP of a gate side. 
         [0013]    The backlight unit  20  includes a lamp unit  21  that generates first light, a reflective plate  23  that reflects the first light generated from the lamp unit  21 , and a light adjusting unit  22  that diffuses the first light to output second light having a uniform luminance distribution. 
         [0014]    The lamp unit  21  includes one or more lamps  212   a , lamp holders  21   b  installed at both end portions facing the one or more lamps  21   a , and an inverter that supplies power to the lamp unit  21 . An inverter PCB  50  having an inverter circuit is covered by a shield cover  60  and fastened to a rear surface of a lower cover  25 . 
         [0015]    The light adjusting unit  22  includes a diffusion plate  22   a , and a first diffusion sheet  22   b , a prism sheet  22   c , a second diffusion sheet  22   d , etc. which are sequentially disposed at an upper side of the diffusion plate  22   a.    
         [0016]    A main support is formed at an upper portion of the backlight unit  20  and at a lower portion of the liquid crystal panel  40 , maintaining the balance of overall power of the LCD. 
         [0017]    The upper cover  40  surrounds the edges of four sides of the liquid crystal panel and is fastened to the lower cover  25  to accommodate the liquid crystal panel  10  and the backlight unit  20 . 
         [0018]      FIG. 2  is a view showing a state that the inverter PCB and the shield cover are fastened to the lower surface of the lower cover, and  FIG. 3  is a sectional view taken along line A-A′ in  FIG. 2 . 
         [0019]    As shown in  FIGS. 2 and 3 , the inverter PCB  50  is disposed at one edge portion of the rear surface of the lower cover  25 , and includes an inverter IC (Integrated Circuit)  50   a  including an integrated element such as an FET, etc., and a transformer  50   b.    
         [0020]    The shield cover  60  is positioned at an upper portion of the inverter PCB  50  to protect the inverter PCB  50  against external static electricity and includes a plurality of holes formed on its surface to externally release heat generated from the lower inverter PCB  50 . 
         [0021]    Recently, as the LCD is increasingly enlarged, it uses more backlights employing a high output transformer for voltage transformation, and in this case, a large amount of magnetic flux is induced to the shield cover  60  to cause eddy current, which results in that the system generates heat of high temperature and much power consumption. 
       SUMMARY OF THE INVENTION 
       [0022]    Therefore, in order to address the above matters the various features described herein have been conceived. One aspect of the exemplary embodiments is to provide a liquid crystal display having a heat releasing structure in which a heat conduction unit is formed on a heating element such as a transformer or an inverter IC formed on an inverter PCB and allowed to contact with a shield cover to thus effectively release heat. 
         [0023]    This specification provides an LCD including: a lower cover; a backlight unit formed on the lower cover and providing light; a liquid crystal panel separated from the backlight unit and provided with light; an inverter PCB that drives the backlight unit; an inverter IC and a transformer mounted on the PCB and generating voltage supplied to the backlight unit; a heat conduction unit attached on the inverter IC and the transformer and heat-conducted; and a shield cover protecting the PCB from the exterior and contacting with the heat conduction unit on the inverter IC and the transformer to release heat. 
         [0024]    This specification also provides an LCD including: a lower cover; a backlight unit formed on the lower cover and providing light; a liquid crystal panel separated from the backlight unit and provided with light; an inverter PCB that drives the backlight unit; an inverter IC and a transformer mounted on the PCB and generating voltage supplied to the backlight unit; a heat conduction unit attached at an upper portion of the inverter IC and at a certain region of an upper portion of a primary voltage side of the transformer and heat-conducted; and a shield cover protecting the PCB against the exterior, contacting with the heat conduction unit on the inverter IC and the transformer to release heat, and having a hole to correspond to a certain region of an upper portion of a secondary voltage side of the transformer. 
         [0025]    The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]      FIG. 1  is an exploded perspective view of a general direct type liquid crystal display (LCD); 
           [0027]      FIG. 2  is a view showing a state that an inverter PCB and a shield cover are fastened to a lower surface of the lower cover; 
           [0028]      FIG. 3  is a sectional view taken along line A-A′ in  FIG. 2 ; 
           [0029]      FIG. 4  is an exploded perspective view of an LCD according to one exemplary embodiment of the present invention; 
           [0030]      FIG. 5  is a sectional view taken along line I-I′ in  FIG. 4 ; 
           [0031]      FIG. 6  is an exploded perspective view of an LCD according to another exemplary embodiment of the present invention; and 
           [0032]      FIG. 7  is a sectional view taken along line II-II′ in  FIG. 6 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0033]    A liquid crystal display (LCD) according to exemplary embodiments of the present invention will now be described. 
         [0034]      FIG. 4  is an exploded perspective view of an LCD according to one exemplary embodiment of the present invention, and  FIG. 5  is a sectional view taken along line I-I′ after the inverter PCB  150  and the shield cover  160  are fastened on the lower cover  125  in  FIG. 4 . 
         [0035]    As shown in  FIG. 4 , a reflective plate  123  for reflecting light from a plurality of lamps  121   a , a light source, to a front side is attached on a lower cover  125  made of aluminum (Al), etc. The reflective plate  123  is made of white polyester film or a film coated with a metal (Ag, Al), etc. Light reflectivity of visible light by the reflective plate  123  is about 90% to 97%, and as the coated film becomes thicker, the reflectivity is increased. 
         [0036]    A lamp unit  121  including lamp holders  121  that fix a plurality of arranged lamps  121   a  is provided on the lower cover  125  with the reflective plate  123  attached thereon. A single lamp holder  121  is used to protect a soldered portion of two lamps  121   a  as a basic unit. 
         [0037]    In case of large-scale LCD TVs, it is known that substantially sixteen lamps are used to be arranged at certain intervals for a 32-inch LCD TV, and substantially twenty lamps are used to be arranged at certain intervals for a 40-inch LCD TV, to achieve high luminance. 
         [0038]    Side supports  110   a  and  110   b  are provided to have the lamp holders  121   b  of the lamp unit  121  provided on the lower cover  125  therein. 
         [0039]    On the side supports  110   a  and  110   b  provided at both sides of the lower cover  125 , there are formed a diffusion plate  122   a  that uniformly distributes light directly provided from the lamps  121   a  or reflected from the reflective plate  123  to the front surface and optical sheets  122   b ,  122   c  and  122   d  that handle other optical supplementary functions. 
         [0040]    When the configuration of a backlight unit  120  is completed, a main support  130  is fastened to an upper portion of the backlight unit  120  to maintain the balance of overall power in the LCD. In this case, the main support  130  includes a step pattern on its upper surface in consideration of a liquid crystal panel  110  to be mounted thereon. 
         [0041]    The liquid crystal panel  110  is mounted on the main support  130 . The liquid crystal panel  110  includes an array substrate on which a thin film transistor (TFTs) is formed as a switching element at each unit pixel, a color filter substrate on which color filters for expressing color are formed, and liquid crystal injected between the two substrates. 
         [0042]    The upper cover  140  is fastened to the lower cover  125  by covering the edges of four sides of the liquid crystal panel  110  and the sides of the main support  130 . 
         [0043]    In order to drive the backlight unit  120 , an inverter PCB  150  having inverter circuits such as an inverter IC  150   a , a transformer  150   b , etc., is fastened to a rear surface of the lower cover  125 . 
         [0044]    Here, the inverter IC  150   a , which is formed by integrating an element such as an FET (Field Effect Transistor), etc., includes a DC/DC converter such as a feedback control circuit that receives DC power from the exterior and converts the same into a DC output voltage to stabilize it, and a switching circuit of a full-bridge type that receives an output voltage from the DC/DC converter and transfers power to the transformer. 
         [0045]    The transformer  150   b  receives a DC voltage from the switching circuit, transforms it into an AC voltage and simultaneously increases the voltage, and drives the lamps  121   a  by supplying power thereto. 
         [0046]    When the lamps  121  are driven, the inverter IC  150   a  and the transformer  150   b  formed on the inverter PCB  150  generate a large amount of heat. 
         [0047]    Thus, as shown in  FIG. 5 , heat conduction members  155  having the same size as the area of the inverter IC  150   a  and the transformer  150   b  are formed on the inverter IC  150   a  and the transformer  150   b . The heat conduction members  155  absorb heat from the inverter IC  150   a  and the transformer  150   b  on the inverter PCB  150  and transfer the heat to a shield cover  160 . 
         [0048]    Preferably, the heat conduction members  155  are made as a pad material having relatively good temperature characteristics fabricated by mixing silicon (Si) and aluminum oxide (Al 2 O 3 ). 
         [0049]    As the heat conduction members  155 , 9880FR-5F™ of 3M may be properly used. 9880FR-5F™ is fabricated by disorderly dispersing (distributing) heat conductive ceramic particles in a pressure sensitive adhesive tape. As soon as the 9880FR-5F™ is bonded, heat conduction is made through the ceramic particles. In addition, the 9880FR-5F™ is excellent dielectric, has high adhesive strength, and can be re-worked (re-operated). 
         [0050]    The shield cover  160  is fastened on the inverter PCB  150  with the heat conduction members  155  attached thereon such that is contacts with the inverter IC  150   a  and the transformer  150   b  on the inverter PCB  150 . 
         [0051]    For example, it is assumed that the transformer  150   b  on the inverter PCB  150  is formed to be higher than the inverter IC  150   a  in terms of component structure. In this case, the overall average height of the shield cover  160  would be set on the basis of the height of the transformer  150   b , and in order to allow the shield cover  160  to contact with the inverter IC  150   a , a bending process should be additionally performed in fabricating the shield cover  160 . 
         [0052]    As shown, a protrusion  160   a  formed at an inner surface of the shield cover  160  contacts with the inverter IC  150   a  on the inverter PCB  150 , and the transformer  150   b  contacts with a bottom surface  160   b  of the shield cover  160 . 
         [0053]    As shown in  FIG. 5 , the inverter PCB  150  is fastened on the rear surface of the lower cover  125 , and the heat conduction members  155  are attached on the inverter IC  150   a  and the transformer  150   b  formed on the inverter PCB  150 . 
         [0054]    Here, the transformer  150   b  is a shielding transformer that prevents magnetic flux from being induced to the shield cover  160 . Although not shown, an upper surface of the transformer  150   b  is covered by a shielding unit of a ferromagnetic substance (Ni—Zn). 
         [0055]    However, the shielding unit is not limited thereto, and the transformer can be shielded by a non-magnetic metal of a paramagnetic substance or a diamagnetic substance. 
         [0056]    Here, the paramagnetic substance refers to a material which is magnetized weakly in a direction of a magnetic field when put into a magnetic field. When the magnetic field is removed, the paramagnetic substance is not magnetized. The paramagnetic substance includes aluminum, tin, platinum, iridium, etc. The diamagnetic substance refers to a material which is magnetized in the opposite direction of the magnetic field by an external magnetic field, including materials excluding metals such as gold, silver, copper, etc. 
         [0057]    Thus, in consideration of a situation that the shield cover  160  that protects the lower cover  125  and the inverter of the LCD is replaced by EGI, the shielding unit can serve to quickly absorb heat generated from the transformer  150   b  and release it outwardly, as well as minimizing the influence by the ferromagnetic substance provided at an ambient portion on the transformer  150   b.    
         [0058]    The shield cover  160  is fastened in contact with the inverter IC  150   a  and the transformer  150   b  with the heat conduction members  155  formed thereon. 
         [0059]    Thus, because the shield cover  160  and the transformer  150   b  contact directly via the heat conduction members  155 , a thermal resistance value can be minimized. This means that the heat release characteristics can be increased by maximizing the heat transfer. 
         [0060]      FIG. 6  is an exploded perspective view of an LCD according to another exemplary embodiment of the present invention, and  FIG. 7  is a sectional view taken along line II-II′ in  FIG. 6 . 
         [0061]    With reference to  FIGS. 6 and 7 , a heat conduction member  255  is formed with certain regions at an upper portion of an inverter IC  250 Aa and at an upper portion of a primary voltage side of a transformer  250   b  on an inverter PCB. 
         [0062]    Here, the transformer  250   b , which is a non-shielding transformer, does not has a shielding unit on its upper end portion, so a secondary high voltage part of the transformer  250   b  and the shield cover  260  cannot contact directly with each other in terms of safety standards. 
         [0063]    If a heat conduction member was formed on the secondary high voltage part of the non-shielding transformer  250   b  and the shielding cover  260  contacted therewith, a short phenomenon would occur between the shield cover  260  and the transformer  250   b . Thus, in the present invention, preferably, a hole  260   b  in a square (or rectangular) shape is formed to correspond to a certain region at an upper portion of a secondary voltage side of the transformer  250   b.    
         [0064]    For example, the region of the transformer  250   b  is divided into two exact halves, one half being the primary voltage side and the other half being the secondary voltage side of the transformer  250   b , and the heat conduction member  255  and the shield cover  260  contacting with the heat conduction member  255  are formed on the primary voltage side transformer  250   b  to release heat outwardly. Meanwhile, the shield cover  260  with the hole  260   b  is positioned on the secondary voltage side transformer  250   b , and the secondary voltage side of the transformer  250   b  is exposed to release heat outwardly. 
         [0065]    Excluding the above-described content, the LCD according to another exemplary embodiment of the present invention is not much different from that of one exemplary embodiment of the present invention, so other detailed content will be replaced by the above-described content. 
         [0066]    As so far described, the LCD according to the present invention has such advantages that because heat generated from heating elements on the inverter PCB can be quickly released outwardly, power consumption at the inverter PCB can be reduced and the efficiency of an input voltage to an output voltage can be increased. 
         [0067]    As the present invention may be embodied in several forms without departing from the characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its scope as defined in the appended claims, and therefore all changes and modifications that fall within the metes and bounds of the claims, or equivalents of such metes and bounds are therefore intended to be embraced by the appended claims.