Patent Publication Number: US-2011075443-A1

Title: Light emitting unit, backlight module and display device

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the priority benefit of Taiwan Patent Application Serial Number 098132675, filed on Sep. 28, 2009, the full disclosure of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     The invention is related to a light emitting unit, and more particularly to a light emitting unit of a backlight module of a display device, wherein the light emitting unit is assembled only by enough normalized light bars in number and a closed-loop terminal. 
     BACKGROUND 
     Referring to  FIG. 1 , it depicts a light emitting diode (LED) type light bar  10  having a single integral body. The LED type light bar  10  can be a light emitting unit of a backlight module of a liquid crystal display device. A plurality of light emitting diodes (LEDs)  12  are mounted on a printed circuit board  16  by a surface mounting technology (SMT) process. A connector  18  is mounted at one end of the printed circuit board  16 . One end of a flexible circuit board  14  is electrically connected with the connector  18 , and the other end of the flexible circuit board is electrically connected with another printed circuit board (not shown) of a liquid crystal display panel of the liquid crystal display device, whereby electrical power is transmitted to energize the LED type light bar  10 . 
     However, according to the LED type light bar of the backlight module of the large-size liquid crystal display device, the LED type light bar having the single integral body must be long, and thus the printed circuit board of the LED type light bar is also long. If the printed circuit board is longer, the yield of the printed circuit board is lower and manufacture cost of the printed circuit board is higher accordingly. 
     Furthermore, according to the LED type light bar (having the single integral body) of the backlight module of the large-size liquid crystal display device, the number of the LEDs of the LED type light bar must be more, and thus the failure probability of the LED type light bar is higher. If the LED type light bar having the single integral body is failed, the whole light bar must be replaced so as to have higher maintenance cost. 
     Accordingly, there exists a need for a light emitting unit capable of solving the above-mentioned problems. 
     SUMMARY 
     The present invention provides a light emitting unit including a light bar set, a connecting mechanism and a closed-loop terminal. The light bar set includes a plurality of light bars, wherein each light bar includes a plurality of light emitting elements and a circuit board, and the light emitting elements are disposed on the circuit board. The connecting mechanism includes a plurality of connecting elements for electrically connecting the first one to the last one of the light bars in order. The connecting mechanism has a front end and a rear end. The closed-loop terminal is electrically connected to the rear end of the connecting mechanism, whereby the light bar set, the connecting mechanism and the closed-loop terminal are formed to a closed loop. 
     According to the light emitting unit of the backlight module of the large-size liquid crystal display device, the present invention provide a light emitting unit which is assembled with enough normalized light bars in number in accordance with design requirement, and thus the light emitting unit of the present invention has no problem of a longer circuit board of the conventional light emitting unit (having the single integral body). Furthermore, the number of the LEDs of the single normalized light bar of the present invention is not more, but enough LEDs in number are shared by a plurality of normalized light bars. Therefore, if a normalized light bar is failed, only the failed normalized light bar is replaced rather than the whole light emitting unit is replaced so as to save material cost. In addition, normalized light bars of the light emitting unit of the present invention are easily manufactured and stocked so as to have lower product cost. 
     The foregoing, as well as additional objects, features and advantages of the invention will be more apparent from the following detailed description, which proceeds with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present invention are illustrated by way of example, and not by limitation, in the figures of the accompanying drawings, wherein elements having the same reference numeral designations represent like elements throughout and wherein: 
         FIG. 1  is a cross-sectional schematic view of a LED type light bar in the prior art; 
         FIG. 2  is a perspective schematic view of a light emitting unit according to the first embodiment of the present invention; 
         FIGS. 3   a  and  3   b  are plan schematic view of a light emitting unit according to an example of the first embodiment of the present invention, showing a normalized light bar before assembly and a light emitting unit after assembly; 
         FIGS. 4   a  and  4   b  are plan schematic view of a light emitting unit according to an alternative example of the first embodiment of the present invention, showing a normalized light bar before assembly and a light emitting unit after assembly; 
         FIGS. 5   a  and  5   b  are plan schematic view of a light emitting unit according to another example of the first embodiment of the present invention, showing a normalized light bar before assembly and a light emitting unit after assembly; 
         FIGS. 6   a  and  6   b  are plan schematic view of a light emitting unit according to another alternative example of the first embodiment of the present invention, showing a normalized light bar before assembly and a light emitting unit after assembly; 
         FIG. 7  is an exploded perspective schematic view of a side light type backlight module according to the first embodiment of the present invention; 
         FIG. 8  is a partially cross-sectional schematic view of a side light type backlight module according to the first embodiment of the present invention; 
         FIG. 9  is an exploded perspective schematic view of a display device according to the first embodiment of the present invention; 
         FIG. 10  is a perspective schematic view of a light emitting unit according to the second embodiment of the present invention; and 
         FIG. 11  is a cross-sectional schematic view of a direct light type backlight module according to the second embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIG. 2 , it depicts a light emitting unit  200  according to the first embodiment of the present invention. The light emitting unit  200  includes a light bar set, a connecting mechanism and a closed-loop terminal  220 . The light bar set includes a plurality of normalized light bars  210 . The light bars  210  are arranged in the one-dimensional direction. Each light bar  210  includes a plurality of light emitting elements  212  and a circuit board  216  (e.g. printed circuit board), and the light emitting elements  212  are disposed on the circuit board  216 . The light emitting elements  212  can be light emitting diodes (LEDs), and can be arranged in the one-dimensional direction. The connecting mechanism includes a plurality of connecting elements  214  for electrically connecting the first light bar  210  to the last light bar  210  in order. The front end  213  of the connecting mechanism is electrically connected to an external circuit board (not shown) and an external power supply device (not shown). The rear end  215  of the connecting mechanism is electrically connected to the closed-loop terminal  220 , whereby the light bars  210  of the light bar set, the connecting elements  214  of the connecting mechanism and the closed-loop terminal  220  are formed to a closed loop so as to energize the LEDs. More detailed, the light bar set can include N light bars  210 , N is an integer being more than one. The connecting mechanism can include N+1 connecting elements  214  for electrically connecting the first one to the N-th one of the light bars  210  and the closed-loop terminal  220  in order. 
     Referring to  FIGS. 3   a  and  3   b , they depict a light emitting unit  200  according to an example of the first embodiment of the present invention showing a normalized light bar  210  before assembly and a light emitting unit  200  after assembly. According to the normalized light bar  210 , each light bar  210  includes a front connector  218  and a rear connector  218  disposed at the front end  218   a  and the rear end  218   b  respectively. The connecting elements  214  of the connecting mechanism are flexible circuit boards  214   a,    214   b,    214   c,  the flexible circuit board  214   a,    214   b,    214   c  has a front end  213 ′ and a rear end  215 ′, wherein the front end  213 ′ of the first flexible circuit board  214   a  is the front end  213  of the connecting mechanism, the rear end  215 ′ of the first flexible circuit board  214   a  is electrically connected with the front connector  218  of the first light bar  210 ; the front end  213 ′ of the second flexible circuit board  214   b  is electrically connected with the rear connector  218  of the first light bar  210 , and the rear end  215 ′ of the second flexible circuit board  214   b  is electrically connected with the front connector  218  of the second light bar  210 ; likewise, the front end  213 ′ of the N-th flexible circuit board  214   b  is electrically connected with the rear connector  218  of the N−1-th light bar  210 , and the rear end  215 ′ of the N-th flexible circuit board  214   b  is electrically connected with the front connector  218  of the N-th light bar  210 ; and the front end  213 ′ of the N+1-th flexible circuit board  214   c  is electrically connected with the rear connector  218  of the N-th light bar  210 , and the rear end  215 ′ of the N+1-th flexible circuit board  214   c  is the rear end  215  of the connecting mechanism. The closed-loop terminal  220  can also include a connector  218 , whereby the rear end  215 ′ of the N+1-th flexible circuit board  214   c  is electrically connected with the connector  218  of the closed-loop terminal  220 . The normalized light bar  210  has a normalized structure being characterized in that a connector  218  is disposed at the rear end  218   b  of the light bar  210  and another connector  218  is disposed at the front end  218   a  of the light bar  210 . 
     Referring to  FIGS. 4   a  and  4   b , they depict a light emitting unit  200  according to an alternative example of the first embodiment of the present invention showing a normalized light bar  210  before assembly and a light emitting unit  200  after assembly. According to the normalized light bar  210 , each light bar  210  has a front end  218   a  and a rear end  218   b,  and includes a rear connector  218  disposed at the rear end  218   b  of the light bar  210  and a flexible circuit boards  214   b  electrically soldered to the front end  218   a  of the light bar  210 . The connecting elements  214  of the connecting mechanism are flexible circuit boards  214   a,    214   b ,  214   c.  The front end  213 ′ of the first flexible circuit board  214   a  is the front end  213  of the connecting mechanism, the rear end  215 ′ of the first flexible circuit board  214   a  is electrically soldered to the front end  218   a  of the first light bar  210 ; the front end  213 ′ of the second flexible circuit board  214   b  is electrically connected with the rear connector  218  of the first light bar  210 , and the rear end  215 ′ of the second flexible circuit board  214   b  is electrically soldered to the front end  218   a  of the second light bar  210 ; likewise, the front end  213 ′ of the N-th flexible circuit board  214   b  is electrically connected with the rear connector  218  of the N−1-th light bar  210 , and the rear end  215 ′ of the N-th flexible circuit board  214   b  is electrically soldered to the front end  218   a  of the N-th light bar  210 ; and the front end  213 ′ of the N+1-th flexible circuit board  214   c  is electrically connected with the rear connector  218  of the N-th light bar  210 , and the rear end  215 ′ of the N+1-th flexible circuit board  214   c  is the rear end  215  of the connecting mechanism. The rear end  215 ′ of the N+1-th flexible circuit board  214   c  can be also electrically soldered to the closed-loop terminal. The normalized light bar  210  has a normalized structure being characterized in that a connector  218  is disposed at the rear end  218   b  of the light bar  210  and a flexible circuit board  214   b  is electrically soldered to the front end  218   a  of the light bar  210 . 
     Referring to  FIGS. 5   a  and  5   b , they depict a light emitting unit  200  according to another example of the first embodiment of the present invention showing a normalized light bar  210  before assembly and a light emitting unit  200  after assembly. According to the normalized light bar  210 , each light bar  210  includes a front plug  228   a  and a rear socket  228   b  disposed at the front end  218   a  and the rear end  218   b  respectively. The connecting elements  214  of the connecting mechanism are flexible flat cables  224   a,    224   b,    224   c,  the flexible flat cable  224   a ,  224   b,    224   c  has a front plug  228   a  and a rear socket  228   b  disposed at the front end  213 ′ and the rear end  215 ′ of the flexible flat cables  224   a,    224   b,    224   c  respectively, the front plug  228   a  of the first flexible flat cable  224   a  is the front end  213  of the connecting mechanism, the rear socket  228   b  of the first flexible flat cable  224   a  is electrically connected with the front plug  228   a  of the first light bar  210 ; the front plug  228   a  of the second flexible flat cable  224   b  is electrically connected with the rear socket  228   b  of the first light bar  210 , and the rear socket  228   b  of the second flexible flat cable  224   b  is electrically connected with the front plug  228   a  of the second light bar  210 ; likewise, the front plug  228   a  of the N-th flexible flat cable  224   b  is electrically connected with the rear socket  228   b  of the N−1-th light bar  210 , and the rear socket  228   b  of the N-th flexible flat cable  224   b  is electrically connected with the front plug  228   a  of the N-th light bar  210 ; and the front plug  228   a  of the N+1-th flexible flat cable  224   c  is electrically connected with the rear socket  228   b  of the N-th light bar  210 , and the rear socket  228   b  of the N+1-th flexible flat cable  224   c  is the rear end  215  of the connecting mechanism. The closed-loop terminal  220  can also include a plug  228   a,  whereby the plug  228   a  of the closed-loop terminal  220  is electrically connected with the rear socket  228   b  of the N+1-th flexible circuit board  224   c . The normalized light bar  210  has a normalized structure being characterized in that a socket  228   b  is disposed at the rear end  218   b  of the light bar  210  and a plug  228   a  is disposed at the front end  218   a  of the light bar  210 . 
     Referring to  FIGS. 6   a  and  6   b , they depict a light emitting unit  200  according to another alternative example of the first embodiment of the present invention showing a normalized light bar  210  before assembly and a light emitting unit  200  after assembly. According to the normalized light bar  210 , each light bar  210  includes a front socket  238   a  and a rear plug  238   b  disposed at the front end  218   a  and the rear end  218   b  respectively. The connecting elements  234  of the connecting mechanism are flexible flat cables  234   a,    234   b,    234   c.  The flexible flat cable  234   a,    234   b,    234   c  includes a front socket  238   a  and a rear plug  238   b  disposed at the front end  213 ′ and the rear end  215 ′ of the flexible flat cable  234   a,    234   b,    234   c  respectively, the front socket  238   a  of the first flexible flat cable  234   a  is the front end  213  of the connecting mechanism, and the rear plug  238   b  of the first flexible flat cable  234   a  is electrically connected with the front socket  238   a  of the first light bar  210 ; the front socket  238   a  of the second flexible flat cable  234   b  are electrically connected with the rear plug  238   b  of the first light bar  210 , and the front socket  238   a  of the second flexible flat cable  234   b  are electrically connected with the rear plug  238   b  of the second light bar  210 ; likewise, the front socket  238   a  of the N-th flexible flat cable  234   b  are electrically connected with the rear plug  238   b  of the N−1-th light bar  210 , and the front socket  238   a  of the N-th flexible flat cable  234   b  are electrically connected with the rear plug  238   b  of the N-th light bar  210 ; and the front socket  238   a  of the N+1-th flexible flat cable  234   c  is electrically connected with the rear plug  238   b  of the N-th light bar  210 , and the rear plug  238   b  of the N+1-th flexible flat cable  234   c  is the rear end  215  of the connecting mechanism. The closed-loop terminal  220  can also include a socket  238   a,  whereby the rear plug  238   b  of the N+1-th flexible circuit board  234   c  is electrically connected with the socket  238   a  of the closed-loop terminal  220 . The normalized light bar  210  has a normalized structure being characterized in that a plug  238   b  is disposed at the rear end  218   b  of the light bar  210  and a socket  238   a  is disposed at the front end  218   a  of the light bar  210 . 
     Referring to  FIG. 7 , it depicts a side light type backlight module  120   a  according to the first embodiment of the present invention, i.e. the light emitting unit  200  can be applied to the side light type backlight module  120   a.  The side light type backlight module  120   a  includes a light guide plate  130 , the light emitting unit  200  of the present invention, a reflector  134  (e.g. U-shaped reflector), a reflecting plate  136  and a plurality of optical films  124 . Referring to  FIG. 8 , the light emitting unit  200  is disposed on at least one side surface  132  of the light guide plate  130 . The reflector  134  surrounds the light emitting unit  200 , and an opening  138  of the reflector  134  faces the side surface  132  of the light guide plate  130  for reflecting lights of the light emitting unit  200  to the light guide plate  130 . The reflecting plate  136  is mounted on a bottom surface of the light guide plate  130 . The optical films  124  (e.g. a diffusing sheet and a prism sheet) are disposed on a top surface of the light guide plate  130 . The backlight module  120   a  further includes a housing  142  and a frame  144 , wherein the housing  142  is assembled with the frame  144 , whereby the light guide plate  130 , the light emitting unit  200 , the reflector  134  and the optical films  124  are mounted between the housing  142  and the frame  144 . 
     Referring to  FIG. 9 , it depicts a display device according to the first embodiment of the present invention, i.e. the backlight module  120   a  can be applied to the display device, e.g. liquid crystal display device  110 . The liquid crystal display device  110  includes a front frame  112 , a display panel (liquid crystal display panel  114 ) and the backlight module  120   a  of the present invention. The liquid crystal display panel  114  has a liquid crystal layer (not shown) disposed between upper and lower substrates (not shown) for displaying images. The liquid crystal display panel  114  includes a printed circuit board  116  and a connector  131  disposed on the printed circuit board  116 . The printed circuit board  116  is adapted to transmit control and driving signals to the liquid crystal display panel  114 . The front end of the connecting element  214  of the connecting mechanism of the light emitting unit  200  of the backlight module  120   a  is electrically connected to the printed circuit board  116  by a connector  131 . In addition, in another embodiment the connecting element  214  can be electrically soldered to the printed circuit board  116  rather than electrically connected to the printed circuit board by a connector. The backlight module  120   a  provides the liquid crystal display panel  114  with a uniform backlight. The backlight module  120   a  is assembled with the front frame  112  for combining the front frame  112 , the liquid crystal display panel  114  and the backlight module  120   a  to a liquid crystal display device  110 . 
     Referring to  FIG. 10 , it depicts a light emitting unit  300  according to the second embodiment of the present invention. The light emitting unit  300  in the second embodiment is similar to the light emitting unit  200  in the first embodiment, wherein the similar elements are designated with the similar reference numerals. The light emitting unit  300  includes a light bar set, a connecting mechanism and a closed-loop terminal  320 . The light bar set includes a plurality of normalized light bars  310 . The light bars  310  are arranged in the two-dimensional direction. Each light bar  310  includes a plurality of light emitting elements  312  and a circuit board  316 , and the light emitting elements  312  are disposed on the circuit board  316 . The light emitting elements  312  can be light emitting diodes (LEDs). In this embodiment, the light emitting elements  312  can be arranged in the two-dimensional direction. In another embodiment, the light emitting elements  312  can be arranged in the one-dimensional direction (not shown). The connecting mechanism includes a plurality of connecting elements  314   a,    314   b,    314   c  for electrically connecting from the first one to the last one of the light bars  310  in order. The front end  313  of the connecting mechanism is electrically connected to an external circuit board (not shown) and an external power supply device (not shown). The rear end  315  of the connecting mechanism is electrically connected to the closed-loop terminal  320 , whereby the light bars  310  of the light bar set, the connecting elements  314  of the connecting mechanism and the closed-loop terminal  320  are formed to a closed loop. More detailed, the light bar set can include N light bars  310 , N is an integer being more than one. The connecting mechanism can include N+1 connecting elements  314  for electrically connecting the first one to the N-th one of the light bars  310  and the closed-loop terminal  320  in order. 
     Similar to four examples of the first embodiment, the normalized light bar in the second embodiment has a normalized structure being characterized in that a connector is disposed at the rear end of the light bar and another connector is disposed at the front end of the light bar. Or, the normalized light bar in the second embodiment has a normalized structure being characterized in that a connector is disposed at the rear end of the light bar and a flexible circuit board is electrically soldered to the front end of the light bar. Or, the normalized light bar in the second embodiment has a normalized structure being characterized in that a socket is disposed at the rear end of the light bar and a plug is disposed at the front end of the light bar. Or, the normalized light bar in the second embodiment has a normalized structure being characterized in that a plug is disposed at the rear end of the light bar and a socket is disposed at the front end of the light bar. 
     Referring to  FIG. 11 , it depicts a direct light type backlight module  120   b  according to the second embodiment of the present invention, i.e. the light emitting unit  300  can be applied to the direct light type backlight module  120   b.  The direct light type backlight module  120   b  includes a housing  122 , the light emitting unit  300  of the present invention, and a plurality of optical films  124 . The housing  122  has a bottom plate  126  for support the light emitting unit  300  and disposing the light emitting unit  300  in the housing  122 . The optical films  124  (e.g. a diffusing sheet and a prism sheet) are disposed above the housing  122 . 
     The backlight module  120   b  can be also applied to the display device, e.g. liquid crystal display device. The liquid crystal display device includes a front frame, a display panel (liquid crystal display panel) and the backlight module  120   b  of the present invention. The liquid crystal display panel includes a printed circuit board and a connector disposed on the printed circuit board. The front end of the connecting element of the connecting mechanism of the light emitting unit of the backlight module  120   b  is electrically connected to the printed circuit board by a connector. In addition, in another embodiment the connecting element can be electrically soldered to the printed circuit board rather than electrically connected to the printed circuit board by a connector. The backlight module  120   b  provides the liquid crystal display panel with a uniform backlight. The backlight module  120   b  is assembled with the front frame for combining the front frame, the liquid crystal display panel and the backlight module  120   b  to a liquid crystal display device. 
     According to the light emitting unit of the backlight module of the large-size liquid crystal display device, the present invention provide a light emitting unit which is assembled with enough normalized light bars in number in accordance with design requirement, and thus the light emitting unit of the present invention has no problem of a longer circuit board of the conventional light emitting unit (having the single integral body). Furthermore, the number of the LEDs of the single normalized light bar of the present invention is not more, but enough LEDs in number are shared by a plurality of normalized light bars. Therefore, if a normalized light bar is failed, only the failed normalized light bar is replaced rather than the whole light emitting unit is replaced so as to save material cost. In addition, normalized light bars of the light emitting unit of the present invention are easily manufactured and stocked so as to have lower product cost. 
     Although the invention has been explained in relation to its preferred embodiment, it is not used to limit the invention. It is to be understood that m any other possible modifications and variations can be made by those skilled in the art without departing from the spirit and scope of the invention as hereinafter claimed.