Patent Publication Number: US-2010128195-A1

Title: Backlight Module and Liquid Crystal Display Device Using the Same

Description:
This application claims priority based on a Taiwanese patent application No. 097145116 filed on Nov. 21, 2008, the disclosure of which is incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a backlight module. Specifically, the present invention relates to a backlight module which can use light-emitting diodes and rework/repair easily. 
     2. Description of the Prior Art 
     Liquid crystal displays (LCDs) are not a self-emitting display device, thus, a backlight module is an essential component to most LCDs. Different backlight module techniques have a decisive impact on the ultimate product in terms of thickness, display quality, environmentally conscious design, power efficiency, product life span, price competitiveness, etc. 
     In the current market, cold cathode fluorescent lamps (CCFLs) are adopted as the backlight source for most LCD devices; however, the CCFLs only display around 70% to 80% of the NTSC (National Television Standards Committee) color gamut. Also, the CCFLs include mercury (Hg), which does not conform to the environmental protection standards of the European Union (EU). For a solution, industries look into the possibility of substituting light emitting diodes (LEDs) for the CCFLs as the backlight source. When using the LEDs as the backlight source, the LCD provides a wider color gamut and better color performance since the LED has characteristics such as delicacy, high brightness, no mercury, high color reproducibility, etc. 
       FIG. 1  and  FIG. 2  show a conventional LCD display device using the LED as a backlight source. The backlight module  10  includes a casing  12 , a light emitting diode module (LED module)  15 , a reflective plate  18 , and a plurality of optical films  20 . The plurality of optical films  20 , the reflective plate  18 , and the LED module  15  are respectively assembled and covered inside the casing  12 . A plurality of light emitting diodes (LEDs)  14  is disposed on the printed circuit board  16 , and a plurality of holes  19  are formed on the reflective plate  18  corresponding to the LEDs  14 , such that each of the holes  19  can penetrate each of the LEDs  14  and attach to the side surface of the LED module  15 . 
     The LEDs  14  should be repaired while the displaying or emitting performance encounters problems such as local dimming, RGB dimming or other reasons, so that the backlight module  10  can provide normal chromaticity. In the reparation, the backlight module  10  must be disassembled element by element to finally take out the LED module  15  from the casing  12 . The aforesaid disassembly process is quite inconvenient and time consuming, especially if the LED  14  only needs to be renewed or adjusted. Therefore, the present invention is provided to improve the aforesaid problems and achieve other objectives. 
     SUMMARY OF THE INVENTION 
     It is an objective of the present invention to provide a backlight module and a display device using the same which can be easily reworked. 
     It is another objective of the present invention to provide a backlight module and a display device using the same which can be directly disposed on a heat dissipation or temperature uniformity element. 
     It is another objective of the present invention to provide a backlight module and a display device that increases light mixing distance. 
     It is another objective of the present invention to provide a backlight module and a display device using the same of a lighter weight. 
     The present invention provides a backlight module including a housing, a reflective sheet, and a light source module. The housing has an inner side surface, an outer side surface, and a plurality of first openings. The reflective sheet is disposed on the inner side surface and has a plurality of second openings corresponding to the first openings. The light source module has a plurality of light sources, wherein the light source module is disposed on the outer side surface, and each of the light sources may penetrate each of the first openings and the second openings. 
     In the preferred embodiment, the housing further has a back wall, and the inner side surface and the outer side surface respectively form two opposite sides of the back wall. Each of the light sources penetrates each of the first openings and the second openings, and a cross-section of each of the light sources along a direction parallel to the housing corresponds to a shape of each of the first openings. In addition, the light source is composed of a printed circuit board with the light sources disposed thereon. When the light source module is mounted on the casing, the printed circuit board is disposed outside the outer side surface of the housing, and an upper surface of the printed circuit board is not exposed in the first openings. 
     The present invention further provides a display device including a front frame and a backlight module. The backlight module is composed of structures of the abovementioned embodiment, which will not mention again. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an exploded view of a conventional backlight module; 
         FIG. 2  illustrates a side view of  FIG. 1 ; 
         FIG. 3  illustrates an exploded view of a backlight module of the present invention; 
         FIG. 4A  illustrates a side view of  FIG. 3 ; 
         FIG. 4B  illustrates another side view of  FIG. 3 ; 
         FIG. 5A  illustrates a schematic view of the backlight module disposed on a heat dissipation unit according to the present invention; 
         FIG. 5B  illustrates another schematic view of the backlight module disposed on the heat dissipation unit according to the present invention; 
         FIG. 6  illustrates an exploded view of a display device according to the present invention; and 
         FIG. 7  illustrates a side view of the display device according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention is a backlight module and a display module using the same, which includes a housing with a plurality of openings such that a plurality of light sources of a light source module can correspond to the openings and be assembled to the housing from outside the housing. In a preferred embodiment, the light source module includes a light emitting diode module (LED module), i.e., the light source includes light emitting diode light sources (LED light sources). The LED light sources can be disposed on the LED module by way of individual LED or modular LED, such as LED light bar or other LED modules. Moreover, the backlight module of the present invention is preferably used in liquid crystal display panels (LCD panels), and preferably applied to large sized LCD panel devices. In other embodiments, however, the backlight module may also apply to traffic signals, car lamps, board of advertisements, or other devices as appropriate. 
       FIG. 3  and  FIG. 4A  illustrate an exploded view and a side view of the backlight module according to the present invention. The backlight module  100  includes a housing  120 , a reflective sheet  130 , a light source module  110 , and a plurality of optical films  150 . The housing  120  has an inner side surface  124 , an outer side surface  126 , and a plurality of first openings  122 . In the embodiment shown in  FIG. 3 , the housing  120  further has a back wall  121 , and the inner side surface  124  and the outer side surface  126  respectively form two opposite sides of the back wall  121 . The housing  120  further has a side casing  128  on the perimeter of the back wall  121  and perpendicular to the inner side surface  124  for covering the optical films  150  or other elements as appropriate. The optical films  150  mentioned here disposed parallel to the reflective sheet and include a diffusion plate, a prism sheet or a brightness enhancement film, etc. to provide such concentration or uniformity of light characteristics. The reflection sheet  130  has a plurality of second openings  132  corresponding to the first openings  122 . In other words, the cross-sectional shape of the first openings  122  is similar to that of the second openings  132 . The reflective plate  130  is disposed on the inner side surface  124  to increase the usability of light by reflection of light. 
     In the present embodiment, the reflective sheet  130  such as polycarbonate sheet is preferably attached to the inner side surface  124  of the housing  120  by glue or other proper fasten methods. Therefore, when relative movement generates between the housing  120  and the light source module  110  such as during disassembly or assembly, the reflective sheet  130  will not interfere the movement of the light source module  110 . Accordingly, such design will increase the convenience during rework or repair. Furthermore, since the housing  120  is provided with a lot of the first openings  122 , the overall weight of the backlight module  100  will be lightened. 
       FIG. 3  shows that the light source module  110  has a plurality of light sources  114 . The abovementioned light sources  114  are light emitting diode (LED) light sources and preferably arranged or composed of a LED light bar or LED module. The light source module  110  is disposed on the outer side surface  126  of the housing  120  in such a way that each of the light sources  114  penetrates each of the first openings  122  and the second openings  132  to protrude out of the inner side surface  124  of the housing  120 . The light source module  110  is composed of a printed circuit board  112  and the light sources  114 , and each of the light sources  114  is mounted and distributed on the printed circuit board  112 . As  FIG. 4A  shows, when the light source module  110  is assembled from the outer side surface  126  of the housing  120  to the housing  120 , the printed circuit board  112  preferably contacts with the outer side surface  126  of the housing  120 , i.e., the printed circuit board  112  is disposed outside the outer side surface  126  of the housing  120 . An upper surface of the printed circuit board  112  that closed to the housing is preferably not exposed in the first openings  122 . Each of the light sources  114  penetrates each of the first openings  122  and second openings  132 , and a cross-section of each of the light sources  114  along a direction parallel to the housing  120  corresponds to a shape of each of the first openings  122  and the second openings  132 . In the embodiment shown in  FIG. 4B , however, when the light source module  110  is assembled from the outer side surface  126  of the housing  120  to the housing  120 , the printed circuit board  112  may maintain a distance with the outer side surface  126  of the housing  120  to increase the heat dissipation rate. 
     In this embodiment, the shape of each of the light sources  114  is preferably rectangular. In other embodiments, however, the shape of each of the light sources  114  may include circular, elliptical, triangular, or other irregular shapes. In other words, the shape of each of the first openings  122  and second openings  132  can change according to the cross-section shape of the light sources  114 . In addition, in the embodiment, by disposing the light source module  110  on the outer side surface  126  of the housing  120  can also increase the light mixing distance of the LED light sources  114 , such that the backlight module  100  is capable of enriching the colors of the flat liquid crystal panel device (LCD device). 
       FIG. 5A  illustrates an embodiment of the present invention which is provided with a heat dissipation unit. The present embodiment still has another advantage. Since the light source module  110  is disposed on the outer side surface  126  of the housing  120  directly, the light source module  110  provides a larger space for the heat dissipation unit  200  (or temperature uniformity element) to be disposed thereon to solve the problems of the heat effect generated by light sources  114  and indirectly affected brilliance, chromaticity, etc. As shown in  FIG. 5A , holes are formed behind each of the light sources  114  of the light source module  110  for the heat dissipation unit  200  such as a heat sink, a radiating tube, a heat pipe, a heat dissipation post, or other heat dissipation elements to be inserted therein. In the embodiment shown in  FIG. 5B , however, the light source module  110  may also dispose the heat sinks  210  on the bottom end of each of the light sources  114 , such that the heat may be dissipated outside the outer side surface  126  of the housing  120  by the heat sinks  210  which contact with the light sources  114 . In other embodiments, a fan can be disposed on the proper location of the light source module  110  to bring heat out of the outer side surface  126  of the housing  120  quickly after the heat is dissipated by the heat dissipation unit  200 . 
     In addition, as shown in  FIG. 5A , the light source module  110  is preferably disposed on the back wall  121  of the housing  120  by screws  300 . In the embodiment shown in  FIG. 5B , however, the light source module  110  may be mounted on the outer side surface  126  of the housing  120  by methods of being engaged, adhered, or pasted. When the light sources  114  become local dimming or otherwise need to be reworked/repaired, the disassembly only requires taking away the screws  300  or other relative elements and detaching the light source module  110  after taken apart from the housing  120  and the reflective sheet  130 . Similarly, when the light source module  110  is assembled to the outer side surface  126  of the housing  120 , each light source  114  penetrates each corresponding first opening  122  and second opening  132  and then fixed by the screws  300  or other relative elements to accomplish the rework/repair easily. 
       FIG. 6  and  FIG. 7  illustrate an exploded view and a side view of a flat panel display device according to the present invention. The present invention further provides a display device  700  including a front frame  720  and a backlight module  100 . In the embodiment shown in  FIG. 6 , the display device  700  further includes a liquid crystal panel  710  for receiving image signals to form images. The liquid crystal panel  710  is disposed between the optical films  150  and the front frame  720 , and then assembled with the backlight module  100 . In the present embodiment, the backlight module  100  is preferably adopted as a direct type LED backlight technology. The light source module  110  of the backlight module  100  can be directly provided with the heat dissipation unit, such as heat sink, radiating tube, etc., to solve the heat dissipation problems. For the structures of the backlight module  100 , please refer to the aforesaid embodiment, they will not be repeated again here. 
     Although the preferred embodiments of the present invention have been described herein, the above description is merely illustrative. Further modification of the invention herein disclosed will occur to those skilled in the respective arts and all such modifications are deemed to be within the scope of the invention as defined by the appended claims.